diff --git a/java/com/google/gerrit/entities/LabelTypes.java b/java/com/google/gerrit/entities/LabelTypes.java
index 1c38c59..55a9976 100644
--- a/java/com/google/gerrit/entities/LabelTypes.java
+++ b/java/com/google/gerrit/entities/LabelTypes.java
@@ -20,6 +20,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 public class LabelTypes {
   protected List<LabelType> labelTypes;
@@ -36,12 +37,12 @@
     return labelTypes;
   }
 
-  public LabelType byLabel(LabelId labelId) {
-    return byLabel().get(labelId.get().toLowerCase());
+  public Optional<LabelType> byLabel(LabelId labelId) {
+    return Optional.ofNullable(byLabel().get(labelId.get().toLowerCase()));
   }
 
-  public LabelType byLabel(String labelName) {
-    return byLabel().get(labelName.toLowerCase());
+  public Optional<LabelType> byLabel(String labelName) {
+    return Optional.ofNullable(byLabel().get(labelName.toLowerCase()));
   }
 
   private Map<String, LabelType> byLabel() {
diff --git a/java/com/google/gerrit/server/PatchSetUtil.java b/java/com/google/gerrit/server/PatchSetUtil.java
index d60bc8f..326ddf4 100644
--- a/java/com/google/gerrit/server/PatchSetUtil.java
+++ b/java/com/google/gerrit/server/PatchSetUtil.java
@@ -151,8 +151,10 @@
 
     ApprovalsUtil approvalsUtil = approvalsUtilProvider.get();
     for (PatchSetApproval ap : approvalsUtil.byPatchSet(notes, change.currentPatchSetId())) {
-      LabelType type = projectState.getLabelTypes(notes).byLabel(ap.label());
-      if (type != null && ap.value() == 1 && type.getFunction() == LabelFunction.PATCH_SET_LOCK) {
+      Optional<LabelType> type = projectState.getLabelTypes(notes).byLabel(ap.label());
+      if (type.isPresent()
+          && ap.value() == 1
+          && type.get().getFunction() == LabelFunction.PATCH_SET_LOCK) {
         return true;
       }
     }
diff --git a/java/com/google/gerrit/server/approval/ApprovalInference.java b/java/com/google/gerrit/server/approval/ApprovalInference.java
index 1efbd37..8d409e5 100644
--- a/java/com/google/gerrit/server/approval/ApprovalInference.java
+++ b/java/com/google/gerrit/server/approval/ApprovalInference.java
@@ -52,6 +52,7 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Map;
+import java.util.Optional;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.revwalk.RevWalk;
 
@@ -397,14 +398,14 @@
       if (resultByUser.contains(psa.label(), psa.accountId())) {
         continue;
       }
-      LabelType type = labelTypes.byLabel(psa.labelId());
+      Optional<LabelType> type = labelTypes.byLabel(psa.labelId());
       // Only compute modified files if there is a relevant label, since this is expensive.
       if (modifiedFiles == null
-          && type != null
-          && type.isCopyAllScoresIfListOfFilesDidNotChange()) {
+          && type.isPresent()
+          && type.get().isCopyAllScoresIfListOfFilesDidNotChange()) {
         modifiedFiles = listModifiedFiles(project, ps, priorPatchSet);
       }
-      if (type == null) {
+      if (!type.isPresent()) {
         logger.atFine().log(
             "approval %d on label %s of patch set %d of change %d cannot be copied"
                 + " to patch set %d because the label no longer exists on project %s",
@@ -416,8 +417,8 @@
             project.getName());
         continue;
       }
-      if (!canCopyBasedOnBooleanLabelConfigs(project, psa, ps.id(), kind, type, modifiedFiles)
-          && !canCopyBasedOnCopyCondition(notes, psa, ps.id(), type, kind)) {
+      if (!canCopyBasedOnBooleanLabelConfigs(project, psa, ps.id(), kind, type.get(), modifiedFiles)
+          && !canCopyBasedOnCopyCondition(notes, psa, ps.id(), type.get(), kind)) {
         continue;
       }
       resultByUser.put(psa.label(), psa.accountId(), psa.copyWithPatchSet(ps.id()));
diff --git a/java/com/google/gerrit/server/approval/ApprovalsUtil.java b/java/com/google/gerrit/server/approval/ApprovalsUtil.java
index b1e85e9..a1cdd99 100644
--- a/java/com/google/gerrit/server/approval/ApprovalsUtil.java
+++ b/java/com/google/gerrit/server/approval/ApprovalsUtil.java
@@ -61,6 +61,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.revwalk.RevWalk;
@@ -299,8 +300,12 @@
     List<PatchSetApproval> cells = new ArrayList<>(approvals.size());
     Date ts = update.getWhen();
     for (Map.Entry<String, Short> vote : approvals.entrySet()) {
-      LabelType lt = labelTypes.byLabel(vote.getKey());
-      cells.add(newApproval(ps.id(), user, lt.getLabelId(), vote.getValue(), ts).build());
+      Optional<LabelType> lt = labelTypes.byLabel(vote.getKey());
+      if (!lt.isPresent()) {
+        throw new BadRequestException(
+            String.format("label \"%s\" is not a configured label", vote.getKey()));
+      }
+      cells.add(newApproval(ps.id(), user, lt.get().getLabelId(), vote.getValue(), ts).build());
     }
     for (PatchSetApproval psa : cells) {
       update.putApproval(psa.label(), psa.value());
@@ -310,11 +315,11 @@
 
   public static void checkLabel(LabelTypes labelTypes, String name, Short value)
       throws BadRequestException {
-    LabelType label = labelTypes.byLabel(name);
-    if (label == null) {
+    Optional<LabelType> label = labelTypes.byLabel(name);
+    if (!label.isPresent()) {
       throw new BadRequestException(String.format("label \"%s\" is not a configured label", name));
     }
-    if (label.getValue(value) == null) {
+    if (label.get().getValue(value) == null) {
       throw new BadRequestException(
           String.format("label \"%s\": %d is not a valid value", name, value));
     }
diff --git a/java/com/google/gerrit/server/change/LabelNormalizer.java b/java/com/google/gerrit/server/change/LabelNormalizer.java
index 30343d4..b5527d7 100644
--- a/java/com/google/gerrit/server/change/LabelNormalizer.java
+++ b/java/com/google/gerrit/server/change/LabelNormalizer.java
@@ -33,6 +33,7 @@
 import com.google.inject.Singleton;
 import java.util.Collection;
 import java.util.List;
+import java.util.Optional;
 
 /**
  * Normalizes votes on labels according to project config.
@@ -101,12 +102,12 @@
         unchanged.add(psa);
         continue;
       }
-      LabelType label = labelTypes.byLabel(psa.labelId());
-      if (label == null) {
+      Optional<LabelType> label = labelTypes.byLabel(psa.labelId());
+      if (!label.isPresent()) {
         deleted.add(psa);
         continue;
       }
-      PatchSetApproval copy = applyTypeFloor(label, psa);
+      PatchSetApproval copy = applyTypeFloor(label.get(), psa);
       if (copy.value() != psa.value()) {
         updated.add(copy);
       } else {
diff --git a/java/com/google/gerrit/server/change/LabelsJson.java b/java/com/google/gerrit/server/change/LabelsJson.java
index acff03c..5ce121b 100644
--- a/java/com/google/gerrit/server/change/LabelsJson.java
+++ b/java/com/google/gerrit/server/change/LabelsJson.java
@@ -57,6 +57,7 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.TreeMap;
 
@@ -103,9 +104,9 @@
     for (SubmitRecord rec : submitRecords(cd)) {
       if (rec.labels != null) {
         for (SubmitRecord.Label r : rec.labels) {
-          LabelType type = labelTypes.byLabel(r.label);
-          if (type != null && (!isMerged || type.isAllowPostSubmit())) {
-            toCheck.put(type.getName(), type);
+          Optional<LabelType> type = labelTypes.byLabel(r.label);
+          if (type.isPresent() && (!isMerged || type.get().isAllowPostSubmit())) {
+            toCheck.put(type.get().getName(), type.get());
           }
         }
       }
@@ -120,18 +121,18 @@
         continue;
       }
       for (SubmitRecord.Label r : rec.labels) {
-        LabelType type = labelTypes.byLabel(r.label);
-        if (type == null || (isMerged && !type.isAllowPostSubmit())) {
+        Optional<LabelType> type = labelTypes.byLabel(r.label);
+        if (!type.isPresent() || (isMerged && !type.get().isAllowPostSubmit())) {
           continue;
         }
 
-        for (LabelValue v : type.getValues()) {
-          boolean ok = can.contains(new LabelPermission.WithValue(type, v));
+        for (LabelValue v : type.get().getValues()) {
+          boolean ok = can.contains(new LabelPermission.WithValue(type.get(), v));
           if (isMerged) {
             if (labels == null) {
               labels = currentLabels(filterApprovalsBy, cd);
             }
-            short prev = labels.getOrDefault(type.getName(), (short) 0);
+            short prev = labels.getOrDefault(type.get().getName(), (short) 0);
             ok &= v.getValue() >= prev;
           }
           if (ok) {
@@ -176,21 +177,21 @@
       setAllApprovals(accountLoader, cd, labels);
     }
     for (Map.Entry<String, LabelWithStatus> e : labels.entrySet()) {
-      LabelType type = labelTypes.byLabel(e.getKey());
-      if (type == null) {
+      Optional<LabelType> type = labelTypes.byLabel(e.getKey());
+      if (!type.isPresent()) {
         continue;
       }
       if (standard) {
         for (PatchSetApproval psa : cd.currentApprovals()) {
-          if (type.matches(psa)) {
+          if (type.get().matches(psa)) {
             short val = psa.value();
             Account.Id accountId = psa.accountId();
-            setLabelScores(accountLoader, type, e.getValue(), val, accountId);
+            setLabelScores(accountLoader, type.get(), e.getValue(), val, accountId);
           }
         }
       }
       if (detailed) {
-        setLabelValues(type, e.getValue());
+        setLabelValues(type.get(), e.getValue());
       }
     }
     return labels;
@@ -261,9 +262,9 @@
         MultimapBuilder.hashKeys().hashSetValues().build();
     for (PatchSetApproval a : cd.currentApprovals()) {
       allUsers.add(a.accountId());
-      LabelType type = labelTypes.byLabel(a.labelId());
-      if (type != null) {
-        labelNames.add(type.getName());
+      Optional<LabelType> type = labelTypes.byLabel(a.labelId());
+      if (type.isPresent()) {
+        labelNames.add(type.get().getName());
         // Not worth the effort to distinguish between votable/non-votable for 0
         // values on closed changes, since they can't vote anyway.
         current.put(a.accountId(), a);
@@ -292,8 +293,8 @@
 
     if (detailed) {
       labels.entrySet().stream()
-          .filter(e -> labelTypes.byLabel(e.getKey()) != null)
-          .forEach(e -> setLabelValues(labelTypes.byLabel(e.getKey()), e.getValue()));
+          .filter(e -> labelTypes.byLabel(e.getKey()).isPresent())
+          .forEach(e -> setLabelValues(labelTypes.byLabel(e.getKey()).get(), e.getValue()));
     }
 
     for (Account.Id accountId : allUsers) {
@@ -308,16 +309,16 @@
         }
       }
       for (PatchSetApproval psa : current.get(accountId)) {
-        LabelType type = labelTypes.byLabel(psa.labelId());
-        if (type == null) {
+        Optional<LabelType> type = labelTypes.byLabel(psa.labelId());
+        if (!type.isPresent()) {
           continue;
         }
 
         short val = psa.value();
-        ApprovalInfo info = byLabel.get(type.getName());
+        ApprovalInfo info = byLabel.get(type.get().getName());
         if (info != null) {
           info.value = Integer.valueOf(val);
-          info.permittedVotingRange = pvr.getOrDefault(type.getName(), null);
+          info.permittedVotingRange = pvr.getOrDefault(type.get().getName(), null);
           info.date = psa.granted();
           info.tag = psa.tag().orElse(null);
           if (psa.postSubmit()) {
@@ -328,7 +329,7 @@
           continue;
         }
 
-        setLabelScores(accountLoader, type, labels.get(type.getName()), val, accountId);
+        setLabelScores(accountLoader, type.get(), labels.get(type.get().getName()), val, accountId);
       }
     }
     return labels;
@@ -428,24 +429,24 @@
       PermissionBackend.ForChange perm = permissionBackend.absentUser(accountId).change(cd);
       Map<String, VotingRangeInfo> pvr = getPermittedVotingRanges(permittedLabels(accountId, cd));
       for (Map.Entry<String, LabelWithStatus> e : labels.entrySet()) {
-        LabelType lt = labelTypes.byLabel(e.getKey());
-        if (lt == null) {
+        Optional<LabelType> lt = labelTypes.byLabel(e.getKey());
+        if (!lt.isPresent()) {
           // Ignore submit record for undefined label; likely the submit rule
           // author didn't intend for the label to show up in the table.
           continue;
         }
         Integer value;
-        VotingRangeInfo permittedVotingRange = pvr.getOrDefault(lt.getName(), null);
+        VotingRangeInfo permittedVotingRange = pvr.getOrDefault(lt.get().getName(), null);
         String tag = null;
         Timestamp date = null;
-        PatchSetApproval psa = current.get(accountId, lt.getName());
+        PatchSetApproval psa = current.get(accountId, lt.get().getName());
         if (psa != null) {
           value = Integer.valueOf(psa.value());
           if (value == 0) {
             // This may be a dummy approval that was inserted when the reviewer
             // was added. Explicitly check whether the user can vote on this
             // label.
-            value = perm.test(new LabelPermission(lt)) ? 0 : null;
+            value = perm.test(new LabelPermission(lt.get())) ? 0 : null;
           }
           tag = psa.tag().orElse(null);
           date = psa.granted();
@@ -456,7 +457,7 @@
           // Either the user cannot vote on this label, or they were added as a
           // reviewer but have not responded yet. Explicitly check whether the
           // user can vote on this label.
-          value = perm.test(new LabelPermission(lt)) ? 0 : null;
+          value = perm.test(new LabelPermission(lt.get())) ? 0 : null;
         }
         addApproval(
             e.getValue().label(),
diff --git a/java/com/google/gerrit/server/change/ReviewerJson.java b/java/com/google/gerrit/server/change/ReviewerJson.java
index d5b74a8..6189708 100644
--- a/java/com/google/gerrit/server/change/ReviewerJson.java
+++ b/java/com/google/gerrit/server/change/ReviewerJson.java
@@ -38,6 +38,7 @@
 import com.google.inject.Singleton;
 import java.util.Collection;
 import java.util.List;
+import java.util.Optional;
 import java.util.TreeMap;
 
 @Singleton
@@ -107,10 +108,8 @@
 
     out.approvals = new TreeMap<>(labelTypes.nameComparator());
     for (PatchSetApproval ca : approvals) {
-      LabelType at = labelTypes.byLabel(ca.labelId());
-      if (at != null) {
-        out.approvals.put(at.getName(), formatValue(ca.value()));
-      }
+      Optional<LabelType> at = labelTypes.byLabel(ca.labelId());
+      at.ifPresent(lt -> out.approvals.put(lt.getName(), formatValue(ca.value())));
     }
 
     // Add dummy approvals for all permitted labels for the user even if they
@@ -125,13 +124,13 @@
         }
         for (SubmitRecord.Label label : rec.labels) {
           String name = label.label;
-          LabelType type = labelTypes.byLabel(name);
-          if (out.approvals.containsKey(name) || type == null) {
+          Optional<LabelType> type = labelTypes.byLabel(name);
+          if (out.approvals.containsKey(name) || !type.isPresent()) {
             continue;
           }
 
           try {
-            perm.check(new LabelPermission(type));
+            perm.check(new LabelPermission(type.get()));
             out.approvals.put(name, formatValue((short) 0));
           } catch (AuthException e) {
             // Do nothing.
diff --git a/java/com/google/gerrit/server/events/EventFactory.java b/java/com/google/gerrit/server/events/EventFactory.java
index 3f988a3..1bb694a 100644
--- a/java/com/google/gerrit/server/events/EventFactory.java
+++ b/java/com/google/gerrit/server/events/EventFactory.java
@@ -71,6 +71,7 @@
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.PersonIdent;
@@ -535,10 +536,8 @@
     a.grantedOn = approval.granted().getTime() / 1000L;
     a.oldValue = null;
 
-    LabelType lt = labelTypes.byLabel(approval.labelId());
-    if (lt != null) {
-      a.description = lt.getName();
-    }
+    Optional<LabelType> lt = labelTypes.byLabel(approval.labelId());
+    lt.ifPresent(l -> a.description = l.getName());
     return a;
   }
 
diff --git a/java/com/google/gerrit/server/events/StreamEventsApiListener.java b/java/com/google/gerrit/server/events/StreamEventsApiListener.java
index 439f53e..edd1928 100644
--- a/java/com/google/gerrit/server/events/StreamEventsApiListener.java
+++ b/java/com/google/gerrit/server/events/StreamEventsApiListener.java
@@ -23,7 +23,6 @@
 import com.google.gerrit.entities.Account;
 import com.google.gerrit.entities.BranchNameKey;
 import com.google.gerrit.entities.Change;
-import com.google.gerrit.entities.LabelType;
 import com.google.gerrit.entities.LabelTypes;
 import com.google.gerrit.entities.PatchSet;
 import com.google.gerrit.entities.Project;
@@ -202,10 +201,7 @@
         a.oldValue = Short.toString(oldApprovals.get(approval.getKey()));
       }
     }
-    LabelType lt = labelTypes.byLabel(approval.getKey());
-    if (lt != null) {
-      a.description = lt.getName();
-    }
+    labelTypes.byLabel(approval.getKey()).ifPresent(lt -> a.description = lt.getName());
     if (approval.getValue() != null) {
       a.value = Short.toString(approval.getValue());
     }
diff --git a/java/com/google/gerrit/server/git/MergeUtil.java b/java/com/google/gerrit/server/git/MergeUtil.java
index 1da14f8..a5ea24d 100644
--- a/java/com/google/gerrit/server/git/MergeUtil.java
+++ b/java/com/google/gerrit/server/git/MergeUtil.java
@@ -600,11 +600,11 @@
       } else if (isVerified(a.labelId())) {
         tag = "Tested-by";
       } else {
-        final LabelType lt = project.getLabelTypes().byLabel(a.labelId());
-        if (lt == null) {
+        final Optional<LabelType> lt = project.getLabelTypes().byLabel(a.labelId());
+        if (!lt.isPresent()) {
           continue;
         }
-        tag = lt.getName();
+        tag = lt.get().getName();
       }
 
       if (!contains(footers, new FooterKey(tag), identbuf.toString())) {
diff --git a/java/com/google/gerrit/server/git/receive/ReplaceOp.java b/java/com/google/gerrit/server/git/receive/ReplaceOp.java
index f00b48eb..b2a31b9 100644
--- a/java/com/google/gerrit/server/git/receive/ReplaceOp.java
+++ b/java/com/google/gerrit/server/git/receive/ReplaceOp.java
@@ -465,10 +465,10 @@
           continue;
         }
 
-        LabelType lt = projectState.getLabelTypes().byLabel(a.labelId());
-        if (lt != null) {
-          current.put(lt.getName(), a);
-        }
+        projectState
+            .getLabelTypes()
+            .byLabel(a.labelId())
+            .ifPresent(l -> current.put(l.getName(), a));
       }
     }
     return current;
diff --git a/java/com/google/gerrit/server/index/change/ChangeField.java b/java/com/google/gerrit/server/index/change/ChangeField.java
index 810cd4d..1ee12fe 100644
--- a/java/com/google/gerrit/server/index/change/ChangeField.java
+++ b/java/com/google/gerrit/server/index/change/ChangeField.java
@@ -605,7 +605,7 @@
     for (PatchSetApproval a : cd.currentApprovals()) {
       if (a.value() != 0 && !a.isLegacySubmit()) {
         allApprovals.add(formatLabel(a.label(), a.value(), a.accountId()));
-        LabelType labelType = cd.getLabelTypes().byLabel(a.labelId());
+        Optional<LabelType> labelType = cd.getLabelTypes().byLabel(a.labelId());
         allApprovals.addAll(getMaxMinAnyLabels(a.label(), a.value(), labelType, a.accountId()));
         if (owners && cd.change().getOwner().equals(a.accountId())) {
           allApprovals.add(formatLabel(a.label(), a.value(), ChangeQueryBuilder.OWNER_ACCOUNT_ID));
@@ -622,13 +622,15 @@
   }
 
   private static List<String> getMaxMinAnyLabels(
-      String label, short labelVal, LabelType labelType, @Nullable Account.Id accountId) {
+      String label, short labelVal, Optional<LabelType> labelType, @Nullable Account.Id accountId) {
     List<String> labels = new ArrayList<>();
-    if (labelVal == labelType.getMaxPositive()) {
-      labels.add(formatLabel(label, MagicLabelValue.MAX.name(), accountId));
-    }
-    if (labelVal == labelType.getMaxNegative()) {
-      labels.add(formatLabel(label, MagicLabelValue.MIN.name(), accountId));
+    if (labelType.isPresent()) {
+      if (labelVal == labelType.get().getMaxPositive()) {
+        labels.add(formatLabel(label, MagicLabelValue.MAX.name(), accountId));
+      }
+      if (labelVal == labelType.get().getMaxNegative()) {
+        labels.add(formatLabel(label, MagicLabelValue.MIN.name(), accountId));
+      }
     }
     labels.add(formatLabel(label, MagicLabelValue.ANY.name(), accountId));
     return labels;
diff --git a/java/com/google/gerrit/server/mail/send/MergedSender.java b/java/com/google/gerrit/server/mail/send/MergedSender.java
index 6af2345..56528df 100644
--- a/java/com/google/gerrit/server/mail/send/MergedSender.java
+++ b/java/com/google/gerrit/server/mail/send/MergedSender.java
@@ -79,14 +79,14 @@
       Table<Account.Id, String, PatchSetApproval> pos = HashBasedTable.create();
       Table<Account.Id, String, PatchSetApproval> neg = HashBasedTable.create();
       for (PatchSetApproval ca : args.approvalsUtil.byPatchSet(changeData.notes(), patchSet.id())) {
-        LabelType lt = labelTypes.byLabel(ca.labelId());
-        if (lt == null) {
+        Optional<LabelType> lt = labelTypes.byLabel(ca.labelId());
+        if (!lt.isPresent()) {
           continue;
         }
         if (ca.value() > 0) {
-          pos.put(ca.accountId(), lt.getName(), ca);
+          pos.put(ca.accountId(), lt.get().getName(), ca);
         } else if (ca.value() < 0) {
-          neg.put(ca.accountId(), lt.getName(), ca);
+          neg.put(ca.accountId(), lt.get().getName(), ca);
         }
       }
 
diff --git a/java/com/google/gerrit/server/patch/SubmitWithStickyApprovalDiff.java b/java/com/google/gerrit/server/patch/SubmitWithStickyApprovalDiff.java
index e33b261..62cfa47 100644
--- a/java/com/google/gerrit/server/patch/SubmitWithStickyApprovalDiff.java
+++ b/java/com/google/gerrit/server/patch/SubmitWithStickyApprovalDiff.java
@@ -18,6 +18,7 @@
 
 import com.google.gerrit.common.data.PatchScript;
 import com.google.gerrit.entities.LabelId;
+import com.google.gerrit.entities.LabelType;
 import com.google.gerrit.entities.Patch;
 import com.google.gerrit.entities.Patch.ChangeType;
 import com.google.gerrit.entities.PatchSet;
@@ -43,6 +44,7 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.stream.Collectors;
 import org.eclipse.jgit.diff.Edit;
 import org.eclipse.jgit.lib.Config;
@@ -242,10 +244,9 @@
       if (!patchSetApproval.label().equals(LabelId.CODE_REVIEW)) {
         continue;
       }
-      if (!projectState
-          .getLabelTypes(notes)
-          .byLabel(patchSetApproval.labelId())
-          .isMaxPositive(patchSetApproval)) {
+      Optional<LabelType> lt =
+          projectState.getLabelTypes(notes).byLabel(patchSetApproval.labelId());
+      if (!lt.isPresent() || !lt.get().isMaxPositive(patchSetApproval)) {
         continue;
       }
       if (patchSetApproval.patchSetId().get() > maxPatchSetId.get()) {
diff --git a/java/com/google/gerrit/server/query/approval/MagicValuePredicate.java b/java/com/google/gerrit/server/query/approval/MagicValuePredicate.java
index 2924e6e..326620d 100644
--- a/java/com/google/gerrit/server/query/approval/MagicValuePredicate.java
+++ b/java/com/google/gerrit/server/query/approval/MagicValuePredicate.java
@@ -23,6 +23,7 @@
 import com.google.inject.assistedinject.Assisted;
 import java.util.Collection;
 import java.util.Objects;
+import java.util.Optional;
 
 /** Predicate that matches patch set approvals we want to copy based on the value. */
 public class MagicValuePredicate extends ApprovalPredicate {
@@ -47,19 +48,23 @@
 
   @Override
   public boolean match(ApprovalContext ctx) {
+    Optional<LabelType> lt =
+        getLabelType(ctx.changeNotes().getProjectName(), ctx.patchSetApproval().labelId());
     short pValue;
     switch (value) {
       case ANY:
         return true;
       case MIN:
-        pValue =
-            getLabelType(ctx.changeNotes().getProjectName(), ctx.patchSetApproval().labelId())
-                .getMaxNegative();
+        if (!lt.isPresent()) {
+          return false;
+        }
+        pValue = lt.get().getMaxNegative();
         break;
       case MAX:
-        pValue =
-            getLabelType(ctx.changeNotes().getProjectName(), ctx.patchSetApproval().labelId())
-                .getMaxPositive();
+        if (!lt.isPresent()) {
+          return false;
+        }
+        pValue = lt.get().getMaxPositive();
         break;
       default:
         throw new IllegalArgumentException("unrecognized label value: " + value);
@@ -67,7 +72,7 @@
     return pValue == ctx.patchSetApproval().value();
   }
 
-  private LabelType getLabelType(Project.NameKey project, LabelId labelId) {
+  private Optional<LabelType> getLabelType(Project.NameKey project, LabelId labelId) {
     return projectCache
         .get(project)
         .orElseThrow(() -> new IllegalStateException(project + " absent"))
diff --git a/java/com/google/gerrit/server/query/change/EqualsLabelPredicate.java b/java/com/google/gerrit/server/query/change/EqualsLabelPredicate.java
index 30d5e2f..ade615c 100644
--- a/java/com/google/gerrit/server/query/change/EqualsLabelPredicate.java
+++ b/java/com/google/gerrit/server/query/change/EqualsLabelPredicate.java
@@ -91,8 +91,8 @@
   }
 
   protected static LabelType type(LabelTypes types, String toFind) {
-    if (types.byLabel(toFind) != null) {
-      return types.byLabel(toFind);
+    if (types.byLabel(toFind).isPresent()) {
+      return types.byLabel(toFind).get();
     }
 
     for (LabelType lt : types.getLabelTypes()) {
diff --git a/java/com/google/gerrit/server/query/change/MagicLabelPredicate.java b/java/com/google/gerrit/server/query/change/MagicLabelPredicate.java
index e3c58e47..2c56322 100644
--- a/java/com/google/gerrit/server/query/change/MagicLabelPredicate.java
+++ b/java/com/google/gerrit/server/query/change/MagicLabelPredicate.java
@@ -87,8 +87,8 @@
   }
 
   protected static LabelType type(LabelTypes types, String toFind) {
-    if (types.byLabel(toFind) != null) {
-      return types.byLabel(toFind);
+    if (types.byLabel(toFind).isPresent()) {
+      return types.byLabel(toFind).get();
     }
 
     for (LabelType lt : types.getLabelTypes()) {
diff --git a/java/com/google/gerrit/server/restapi/change/DeleteVote.java b/java/com/google/gerrit/server/restapi/change/DeleteVote.java
index 84424a8..2c358d0 100644
--- a/java/com/google/gerrit/server/restapi/change/DeleteVote.java
+++ b/java/com/google/gerrit/server/restapi/change/DeleteVote.java
@@ -194,7 +194,7 @@
       for (PatchSetApproval a :
           approvalsUtil.byPatchSetUser(
               ctx.getNotes(), psId, accountId, ctx.getRevWalk(), ctx.getRepoView().getConfig())) {
-        if (labelTypes.byLabel(a.labelId()) == null) {
+        if (!labelTypes.byLabel(a.labelId()).isPresent()) {
           continue; // Ignore undefined labels.
         } else if (!a.label().equals(label)) {
           // Populate map for non-matching labels, needed by VoteDeleted.
diff --git a/java/com/google/gerrit/server/restapi/change/Move.java b/java/com/google/gerrit/server/restapi/change/Move.java
index 9263971..8c21841 100644
--- a/java/com/google/gerrit/server/restapi/change/Move.java
+++ b/java/com/google/gerrit/server/restapi/change/Move.java
@@ -64,6 +64,7 @@
 import com.google.inject.Provider;
 import com.google.inject.Singleton;
 import java.io.IOException;
+import java.util.Optional;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
@@ -265,11 +266,13 @@
           approvalsUtil.byPatchSet(
               ctx.getNotes(), psId, ctx.getRevWalk(), ctx.getRepoView().getConfig())) {
         ProjectState projectState = projectCache.get(project).orElseThrow(illegalState(project));
-        LabelType type = projectState.getLabelTypes(ctx.getNotes()).byLabel(psa.labelId());
+        Optional<LabelType> type =
+            projectState.getLabelTypes(ctx.getNotes()).byLabel(psa.labelId());
         // Only keep veto votes, defined as votes where:
         // 1- the label function allows minimum values to block submission.
         // 2- the vote holds the minimum value.
-        if (type == null || (type.isMaxNegative(psa) && type.getFunction().isBlock())) {
+        if (!type.isPresent()
+            || (type.get().isMaxNegative(psa) && type.get().getFunction().isBlock())) {
           continue;
         }
 
diff --git a/java/com/google/gerrit/server/restapi/change/PostReview.java b/java/com/google/gerrit/server/restapi/change/PostReview.java
index 6816361..4dbb6ee 100644
--- a/java/com/google/gerrit/server/restapi/change/PostReview.java
+++ b/java/com/google/gerrit/server/restapi/change/PostReview.java
@@ -22,7 +22,6 @@
 import static com.google.gerrit.server.permissions.LabelPermission.ForUser.ON_BEHALF_OF;
 import static com.google.gerrit.server.project.ProjectCache.illegalState;
 import static java.nio.charset.StandardCharsets.UTF_8;
-import static java.util.Objects.requireNonNull;
 import static java.util.stream.Collectors.groupingBy;
 import static java.util.stream.Collectors.joining;
 import static java.util.stream.Collectors.toList;
@@ -502,8 +501,8 @@
     Iterator<Map.Entry<String, Short>> itr = in.labels.entrySet().iterator();
     while (itr.hasNext()) {
       Map.Entry<String, Short> ent = itr.next();
-      LabelType type = labelTypes.byLabel(ent.getKey());
-      if (type == null) {
+      Optional<LabelType> type = labelTypes.byLabel(ent.getKey());
+      if (!type.isPresent()) {
         logger.atFine().log("label %s not found", ent.getKey());
         if (strictLabels) {
           throw new BadRequestException(
@@ -518,15 +517,15 @@
         logger.atFine().log(
             "skipping on behalf of permission check for label %s"
                 + " because caller is an internal user",
-            type.getName());
+            type.get().getName());
       } else {
         try {
-          perm.check(new LabelPermission.WithValue(ON_BEHALF_OF, type, ent.getValue()));
+          perm.check(new LabelPermission.WithValue(ON_BEHALF_OF, type.get(), ent.getValue()));
         } catch (AuthException e) {
           throw new AuthException(
               String.format(
                   "not permitted to modify label \"%s\" on behalf of \"%s\"",
-                  type.getName(), in.onBehalfOf),
+                  type.get().getName(), in.onBehalfOf),
               e);
         }
       }
@@ -558,8 +557,8 @@
     Iterator<Map.Entry<String, Short>> itr = labels.entrySet().iterator();
     while (itr.hasNext()) {
       Map.Entry<String, Short> ent = itr.next();
-      LabelType lt = labelTypes.byLabel(ent.getKey());
-      if (lt == null) {
+      Optional<LabelType> lt = labelTypes.byLabel(ent.getKey());
+      if (!lt.isPresent()) {
         logger.atFine().log("label %s not found", ent.getKey());
         if (strictLabels) {
           throw new BadRequestException(
@@ -576,7 +575,7 @@
         continue;
       }
 
-      if (lt.getValue(ent.getValue()) == null) {
+      if (lt.get().getValue(ent.getValue()) == null) {
         logger.atFine().log("label value %s not found", ent.getValue());
         if (strictLabels) {
           throw new BadRequestException(
@@ -590,10 +589,10 @@
 
       short val = ent.getValue();
       try {
-        perm.check(new LabelPermission.WithValue(lt, val));
+        perm.check(new LabelPermission.WithValue(lt.get(), val));
       } catch (AuthException e) {
         throw new AuthException(
-            String.format("Applying label \"%s\": %d is restricted", lt.getName(), val), e);
+            String.format("Applying label \"%s\": %d is restricted", lt.get().getName(), val), e);
       }
     }
   }
@@ -1356,7 +1355,10 @@
       ChangeUpdate update = ctx.getUpdate(psId);
       for (Map.Entry<String, Short> ent : allApprovals.entrySet()) {
         String name = ent.getKey();
-        LabelType lt = requireNonNull(labelTypes.byLabel(name), name);
+        LabelType lt =
+            labelTypes
+                .byLabel(name)
+                .orElseThrow(() -> new IllegalStateException("no label config for " + name));
 
         PatchSetApproval c = current.remove(lt.getName());
         String normName = lt.getName();
@@ -1448,7 +1450,10 @@
       List<String> disallowed = new ArrayList<>(labelTypes.getLabelTypes().size());
 
       for (PatchSetApproval psa : del) {
-        LabelType lt = requireNonNull(labelTypes.byLabel(psa.label()));
+        LabelType lt =
+            labelTypes
+                .byLabel(psa.label())
+                .orElseThrow(() -> new IllegalStateException("no label config for " + psa.label()));
         String normName = lt.getName();
         if (!lt.isAllowPostSubmit()) {
           disallowed.add(normName);
@@ -1460,7 +1465,10 @@
       }
 
       for (PatchSetApproval psa : ups) {
-        LabelType lt = requireNonNull(labelTypes.byLabel(psa.label()));
+        LabelType lt =
+            labelTypes
+                .byLabel(psa.label())
+                .orElseThrow(() -> new IllegalStateException("no label config for " + psa.label()));
         String normName = lt.getName();
         if (!lt.isAllowPostSubmit()) {
           disallowed.add(normName);
@@ -1508,9 +1516,9 @@
           continue;
         }
 
-        LabelType lt = labelTypes.byLabel(a.labelId());
-        if (lt != null) {
-          current.put(lt.getName(), a);
+        Optional<LabelType> lt = labelTypes.byLabel(a.labelId());
+        if (lt.isPresent()) {
+          current.put(lt.get().getName(), a);
         } else {
           del.add(a);
         }
diff --git a/java/gerrit/PRED__load_commit_labels_1.java b/java/gerrit/PRED__load_commit_labels_1.java
index 5ee292ff..9a656b8 100644
--- a/java/gerrit/PRED__load_commit_labels_1.java
+++ b/java/gerrit/PRED__load_commit_labels_1.java
@@ -16,6 +16,7 @@
 import com.googlecode.prolog_cafe.lang.StructureTerm;
 import com.googlecode.prolog_cafe.lang.SymbolTerm;
 import com.googlecode.prolog_cafe.lang.Term;
+import java.util.Optional;
 
 /** Exports list of {@code commit_label( label('Code-Review', 2), user(12345789) )}. */
 class PRED__load_commit_labels_1 extends Predicate.P1 {
@@ -38,13 +39,14 @@
     LabelTypes types = cd.getLabelTypes();
 
     for (PatchSetApproval a : cd.currentApprovals()) {
-      LabelType t = types.byLabel(a.labelId());
-      if (t == null) {
+      Optional<LabelType> t = types.byLabel(a.labelId());
+      if (!t.isPresent()) {
         continue;
       }
 
       StructureTerm labelTerm =
-          new StructureTerm(sym_label, SymbolTerm.intern(t.getName()), new IntegerTerm(a.value()));
+          new StructureTerm(
+              sym_label, SymbolTerm.intern(t.get().getName()), new IntegerTerm(a.value()));
 
       StructureTerm userTerm = new StructureTerm(sym_user, new IntegerTerm(a.accountId().get()));
 
diff --git a/javatests/com/google/gerrit/server/schema/SchemaCreatorImplTest.java b/javatests/com/google/gerrit/server/schema/SchemaCreatorImplTest.java
index fc6b412..9cba362 100644
--- a/javatests/com/google/gerrit/server/schema/SchemaCreatorImplTest.java
+++ b/javatests/com/google/gerrit/server/schema/SchemaCreatorImplTest.java
@@ -72,7 +72,7 @@
 
   @Test
   public void createSchema_Label_CodeReview() throws Exception {
-    LabelType codeReview = getLabelTypes().byLabel("Code-Review");
+    LabelType codeReview = getLabelTypes().byLabel("Code-Review").get();
     assertThat(codeReview).isNotNull();
     assertThat(codeReview.getName()).isEqualTo("Code-Review");
     assertThat(codeReview.getDefaultValue()).isEqualTo(0);
diff --git a/plugins/reviewnotes b/plugins/reviewnotes
index 35e6449..a28ae59 160000
--- a/plugins/reviewnotes
+++ b/plugins/reviewnotes
@@ -1 +1 @@
-Subproject commit 35e6449a517691a880c94e7467bc07360f8e6666
+Subproject commit a28ae590486934690e4e0a95d7eb75f8b60644a6