diff --git a/java/com/google/gerrit/plugins/checks/PostCheck.java b/java/com/google/gerrit/plugins/checks/PostCheck.java
index c5e2c02..9b78e07 100644
--- a/java/com/google/gerrit/plugins/checks/PostCheck.java
+++ b/java/com/google/gerrit/plugins/checks/PostCheck.java
@@ -17,6 +17,7 @@
 import com.google.gerrit.extensions.restapi.BadRequestException;
 import com.google.gerrit.extensions.restapi.RestApiException;
 import com.google.gerrit.extensions.restapi.RestCollectionModifyView;
+import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
 import com.google.gerrit.plugins.checks.api.CheckInfo;
 import com.google.gerrit.plugins.checks.api.CheckInput;
 import com.google.gerrit.plugins.checks.api.CheckResource;
@@ -30,12 +31,14 @@
 import javax.inject.Inject;
 import javax.inject.Provider;
 import javax.inject.Singleton;
+import org.eclipse.jgit.errors.ConfigInvalidException;
 
 @Singleton
 public class PostCheck
     implements RestCollectionModifyView<RevisionResource, CheckResource, CheckInput> {
   private final PermissionBackend permissionBackend;
   private final AdministrateCheckersPermission permission;
+  private final Checkers checkers;
   private final Checks checks;
   private final Provider<ChecksUpdate> checksUpdate;
   private final CheckJson checkJson;
@@ -44,11 +47,13 @@
   PostCheck(
       PermissionBackend permissionBackend,
       AdministrateCheckersPermission permission,
+      Checkers checkers,
       Checks checks,
       @UserInitiated Provider<ChecksUpdate> checksUpdate,
       CheckJson checkJson) {
     this.permissionBackend = permissionBackend;
     this.permission = permission;
+    this.checkers = checkers;
     this.checks = checks;
     this.checksUpdate = checksUpdate;
     this.checkJson = checkJson;
@@ -56,7 +61,8 @@
 
   @Override
   public CheckInfo apply(RevisionResource rsrc, CheckInput input)
-      throws OrmException, IOException, RestApiException, PermissionBackendException {
+      throws OrmException, IOException, RestApiException, PermissionBackendException,
+          ConfigInvalidException {
     if (input == null) {
       input = new CheckInput();
     }
@@ -64,14 +70,20 @@
       throw new BadRequestException("checker UUID is required");
     }
     if (!CheckerUuid.isUuid(input.checkerUuid)) {
-      throw new BadRequestException("invalid checker UUID: " + input.checkerUuid);
+      throw new BadRequestException(String.format("invalid checker UUID: %s", input.checkerUuid));
     }
 
     permissionBackend.currentUser().check(permission);
 
-    CheckKey key =
-        CheckKey.create(
-            rsrc.getProject(), rsrc.getPatchSet().getId(), CheckerUuid.parse(input.checkerUuid));
+    CheckerUuid checkerUuid = CheckerUuid.parse(input.checkerUuid);
+    checkers
+        .getChecker(checkerUuid)
+        .orElseThrow(
+            () ->
+                new UnprocessableEntityException(
+                    String.format("checker %s not found", checkerUuid)));
+
+    CheckKey key = CheckKey.create(rsrc.getProject(), rsrc.getPatchSet().getId(), checkerUuid);
     Optional<Check> check = checks.getCheck(key);
     if (!check.isPresent()) {
       if (input.state == null) {
diff --git a/java/com/google/gerrit/plugins/checks/api/UpdateCheck.java b/java/com/google/gerrit/plugins/checks/api/UpdateCheck.java
index 259c5ca..df517f4 100644
--- a/java/com/google/gerrit/plugins/checks/api/UpdateCheck.java
+++ b/java/com/google/gerrit/plugins/checks/api/UpdateCheck.java
@@ -23,6 +23,7 @@
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import java.io.IOException;
+import org.eclipse.jgit.errors.ConfigInvalidException;
 
 @Singleton
 public class UpdateCheck implements RestModifyView<CheckResource, CheckInput> {
@@ -35,7 +36,8 @@
 
   @Override
   public CheckInfo apply(CheckResource checkResource, CheckInput input)
-      throws RestApiException, IOException, OrmException, PermissionBackendException {
+      throws RestApiException, IOException, OrmException, PermissionBackendException,
+          ConfigInvalidException {
     if (input == null) {
       input = new CheckInput();
     }
diff --git a/javatests/com/google/gerrit/plugins/checks/acceptance/api/CreateCheckIT.java b/javatests/com/google/gerrit/plugins/checks/acceptance/api/CreateCheckIT.java
index d354ce5..b3591a7 100644
--- a/javatests/com/google/gerrit/plugins/checks/acceptance/api/CreateCheckIT.java
+++ b/javatests/com/google/gerrit/plugins/checks/acceptance/api/CreateCheckIT.java
@@ -20,6 +20,7 @@
 import com.google.gerrit.acceptance.testsuite.request.RequestScopeOperations;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.BadRequestException;
+import com.google.gerrit.extensions.restapi.UnprocessableEntityException;
 import com.google.gerrit.plugins.checks.CheckKey;
 import com.google.gerrit.plugins.checks.CheckerUuid;
 import com.google.gerrit.plugins.checks.acceptance.AbstractCheckersTest;
@@ -98,6 +99,17 @@
   }
 
   @Test
+  public void cannotCreateCheckForNonExistingChecker() throws Exception {
+    CheckInput input = new CheckInput();
+    input.checkerUuid = "foo:non-existing";
+    input.state = CheckState.RUNNING;
+
+    exception.expect(UnprocessableEntityException.class);
+    exception.expectMessage("checker " + input.checkerUuid + " not found");
+    checksApiFactory.revision(patchSetId).create(input);
+  }
+
+  @Test
   public void cannotCreateCheckWithoutAdministrateCheckers() throws Exception {
     requestScopeOperations.setApiUser(user.getId());