diff --git a/java/com/google/gerrit/plugins/checks/api/UpdateCheck.java b/java/com/google/gerrit/plugins/checks/api/UpdateCheck.java
index fb5b653..2b24640 100644
--- a/java/com/google/gerrit/plugins/checks/api/UpdateCheck.java
+++ b/java/com/google/gerrit/plugins/checks/api/UpdateCheck.java
@@ -46,7 +46,7 @@
     } else if (!checkResource.getCheckerUuid().get().equals(input.checkerUuid)) {
       throw new BadRequestException(
           String.format(
-              "checkerUuid must either be null or the same as on the resource:\n"
+              "checker UUID in input must either be null or the same as on the resource:\n"
                   + "the check resource belongs to checker %s,"
                   + " but in the input checker %s was specified",
               checkResource.getCheckerUuid(), input.checkerUuid));
diff --git a/java/com/google/gerrit/plugins/checks/db/NoteDbCheck.java b/java/com/google/gerrit/plugins/checks/db/NoteDbCheck.java
index c29d3e5..8f6482a 100644
--- a/java/com/google/gerrit/plugins/checks/db/NoteDbCheck.java
+++ b/java/com/google/gerrit/plugins/checks/db/NoteDbCheck.java
@@ -67,7 +67,7 @@
       started = update.started().get();
       modified = true;
     }
-    if (update.finished().isPresent() && update.finished().get().equals(finished)) {
+    if (update.finished().isPresent() && !update.finished().get().equals(finished)) {
       finished = update.finished().get();
       modified = true;
     }
diff --git a/javatests/com/google/gerrit/plugins/checks/acceptance/api/UpdateCheckIT.java b/javatests/com/google/gerrit/plugins/checks/acceptance/api/UpdateCheckIT.java
index a671b18..c356056 100644
--- a/javatests/com/google/gerrit/plugins/checks/acceptance/api/UpdateCheckIT.java
+++ b/javatests/com/google/gerrit/plugins/checks/acceptance/api/UpdateCheckIT.java
@@ -18,6 +18,7 @@
 
 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.plugins.checks.CheckKey;
 import com.google.gerrit.plugins.checks.CheckerUuid;
 import com.google.gerrit.plugins.checks.acceptance.AbstractCheckersTest;
@@ -27,6 +28,7 @@
 import com.google.gerrit.plugins.checks.api.CheckState;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.server.util.time.TimeUtil;
 import com.google.gerrit.testing.TestTimeUtil;
 import com.google.inject.Inject;
 import java.sql.Timestamp;
@@ -69,6 +71,52 @@
   }
 
   @Test
+  public void cannotUpdateCheckerUuid() throws Exception {
+    CheckInput input = new CheckInput();
+    input.checkerUuid = "foo:bar";
+
+    exception.expect(BadRequestException.class);
+    exception.expectMessage(
+        "checker UUID in input must either be null or the same as on the resource");
+    checksApiFactory.revision(patchSetId).id(checkKey.checkerUuid()).update(input);
+  }
+
+  @Test
+  public void specifyingCheckerUuidInInputThatMatchesTheCheckerUuidInTheUrlIsOkay()
+      throws Exception {
+    CheckInput input = new CheckInput();
+    input.checkerUuid = checkKey.checkerUuid().get();
+    checksApiFactory.revision(patchSetId).id(checkKey.checkerUuid()).update(input);
+  }
+
+  @Test
+  public void updateUrl() throws Exception {
+    CheckInput input = new CheckInput();
+    input.url = "http://example.com/my-check";
+
+    CheckInfo info = checksApiFactory.revision(patchSetId).id(checkKey.checkerUuid()).update(input);
+    assertThat(info.url).isEqualTo(input.url);
+  }
+
+  @Test
+  public void updateStarted() throws Exception {
+    CheckInput input = new CheckInput();
+    input.started = TimeUtil.nowTs();
+
+    CheckInfo info = checksApiFactory.revision(patchSetId).id(checkKey.checkerUuid()).update(input);
+    assertThat(info.started).isEqualTo(input.started);
+  }
+
+  @Test
+  public void updateFinished() throws Exception {
+    CheckInput input = new CheckInput();
+    input.finished = TimeUtil.nowTs();
+
+    CheckInfo info = checksApiFactory.revision(patchSetId).id(checkKey.checkerUuid()).update(input);
+    assertThat(info.finished).isEqualTo(input.finished);
+  }
+
+  @Test
   public void updateResultsInNewUpdatedTimestamp() throws Exception {
     CheckInput input = new CheckInput();
     input.state = CheckState.FAILED;