diff --git a/BUILD b/BUILD
index 03f8e0a..401da87 100644
--- a/BUILD
+++ b/BUILD
@@ -42,5 +42,6 @@
     exports = PLUGIN_DEPS + PLUGIN_TEST_DEPS + [
         ":its-base__plugin",
         ":its-base_tests-utils",
+        "@mockito//jar",
     ],
 )
diff --git a/external_plugin_deps.bzl b/external_plugin_deps.bzl
new file mode 100644
index 0000000..5eafc37
--- /dev/null
+++ b/external_plugin_deps.bzl
@@ -0,0 +1,33 @@
+load("//tools/bzl:maven_jar.bzl", "maven_jar")
+
+def external_plugin_deps():
+    maven_jar(
+        name = "mockito",
+        artifact = "org.mockito:mockito-core:2.27.0",
+        sha1 = "835fc3283b481f4758b8ef464cd560c649c08b00",
+        deps = [
+            "@byte-buddy//jar",
+            "@byte-buddy-agent//jar",
+            "@objenesis//jar",
+        ],
+    )
+
+    BYTE_BUDDY_VER = "1.9.10"
+
+    maven_jar(
+        name = "byte-buddy",
+        artifact = "net.bytebuddy:byte-buddy:" + BYTE_BUDDY_VER,
+        sha1 = "211a2b4d3df1eeef2a6cacf78d74a1f725e7a840",
+    )
+
+    maven_jar(
+        name = "byte-buddy-agent",
+        artifact = "net.bytebuddy:byte-buddy-agent:" + BYTE_BUDDY_VER,
+        sha1 = "9674aba5ee793e54b864952b001166848da0f26b",
+    )
+
+    maven_jar(
+        name = "objenesis",
+        artifact = "org.objenesis:objenesis:2.6",
+        sha1 = "639033469776fd37c08358c6b92a4761feb2af4b",
+    )
diff --git a/src/main/java/com/googlesource/gerrit/plugins/its/base/util/CommitMessageFetcher.java b/src/main/java/com/googlesource/gerrit/plugins/its/base/util/CommitMessageFetcher.java
index 905a2a3..7066f59 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/its/base/util/CommitMessageFetcher.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/its/base/util/CommitMessageFetcher.java
@@ -7,6 +7,7 @@
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevObject;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -21,22 +22,33 @@
     this.repoManager = repoManager;
   }
 
-  public String fetch(String projectName, String commitId) throws IOException {
+  public String fetch(String projectName, String objectId) throws IOException {
     try (Repository repo = repoManager.openRepository(new NameKey(projectName))) {
       try (RevWalk revWalk = new RevWalk(repo)) {
-        RevCommit commit = revWalk.parseCommit(ObjectId.fromString(commitId));
-        return commit.getFullMessage();
+        RevObject obj = revWalk.peel(revWalk.parseAny(ObjectId.fromString(objectId)));
+        if (obj instanceof RevCommit) {
+          return ((RevCommit) obj).getFullMessage();
+        }
+        // objectId was found, but it's not a commit.
+        // Since the objectId was found, it's nothing to worry about and we do not need to alert the
+        // user. We silently return the empty string as blobs, trees, ... do not have a proper
+        // commit message.
+        //
+        // Parsing a non-commit objectId (and reaching this point) will happen for example on NoteDB
+        // sites when Gerrit updates `refs/sequences/changes` (which does not point at a commit, but
+        // a blob) on All-Projects and the corresponding RefUpdatedEvent gets processed.
+        return "";
       }
     }
   }
 
-  public String fetchGuarded(String projectName, String commitId) {
+  public String fetchGuarded(String projectName, String objectId) {
     String ret = "";
     try {
-      ret = fetch(projectName, commitId);
+      ret = fetch(projectName, objectId);
     } catch (IOException e) {
       log.error(
-          "Could not fetch commit message for commit " + commitId + " of project " + projectName,
+          "Could not fetch commit message for commit " + objectId + " of project " + projectName,
           e);
     }
     return ret;
diff --git a/src/test/java/com/googlesource/gerrit/plugins/its/base/util/CommitMessageFetcherTest.java b/src/test/java/com/googlesource/gerrit/plugins/its/base/util/CommitMessageFetcherTest.java
new file mode 100644
index 0000000..e833951
--- /dev/null
+++ b/src/test/java/com/googlesource/gerrit/plugins/its/base/util/CommitMessageFetcherTest.java
@@ -0,0 +1,160 @@
+// Copyright (C) 2020 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.googlesource.gerrit.plugins.its.base.util;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.googlesource.gerrit.plugins.its.base.testutil.LoggingMockingTestCase;
+import java.io.IOException;
+import java.math.BigInteger;
+import java.util.HashSet;
+import java.util.Set;
+import org.eclipse.jgit.errors.MissingObjectException;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectLoader;
+import org.eclipse.jgit.lib.ObjectReader;
+import org.eclipse.jgit.lib.Repository;
+import org.junit.Test;
+
+public class CommitMessageFetcherTest extends LoggingMockingTestCase {
+  private GitRepositoryManager repoManager;
+  private Repository repo;
+  private String objectIdBlob = "24c5735c3e8ce8fd18d312e9e58149a62236c01a";
+  private String objectIdTree = "3faaefce19558dfc8d9c976f09ae4897f45cb242";
+  private String objectIdCommit = "95aed53c03b6d3df0912bdd9bb1d0c6eaf619f58";
+  private String objectIdMissing = "0123456789012345678901234567890123456789";
+
+  private byte rawBlob[] = "def\n".getBytes();
+  private byte rawTree[] = sha1append("100644 abc\000", objectIdBlob);
+  private byte rawCommit[] =
+      ("tree\0003faaefce19558dfc8d9c976f09ae4897f45cb242\n"
+              + "author Author <author@example.org> 1592579853 +0200\n"
+              + "committer Committer <committer@example.org> 1592579853 +0200\n"
+              + "\n"
+              + "CommitMsg\n")
+          .getBytes();
+
+  private static byte[] sha1append(String left, String sha1sum) {
+    int leftLen = left.length();
+    byte[] right = (new BigInteger(sha1sum, 16)).toByteArray();
+    byte[] ret = new byte[leftLen + right.length];
+    System.arraycopy(left.getBytes(), 0, ret, 0, leftLen);
+    System.arraycopy(right, 0, ret, leftLen, right.length);
+    return ret;
+  }
+
+  @Test
+  public void testFetchBlob() throws IOException {
+    CommitMessageFetcher fetcher = createCommitMessageFetcher();
+    String commitMessage = fetcher.fetch("ProjectFoo", objectIdBlob);
+
+    assertThat(commitMessage).isEmpty();
+  }
+
+  @Test
+  public void testFetchTree() throws IOException {
+    CommitMessageFetcher fetcher = createCommitMessageFetcher();
+    String commitMessage = fetcher.fetch("ProjectFoo", objectIdTree);
+
+    assertThat(commitMessage).isEmpty();
+  }
+
+  @Test
+  public void testFetchCommit() throws IOException {
+    CommitMessageFetcher fetcher = createCommitMessageFetcher();
+    String commitMessage = fetcher.fetch("ProjectFoo", objectIdCommit);
+
+    assertThat(commitMessage).isEqualTo("CommitMsg\n");
+  }
+
+  @Test
+  public void testFetchGuardedBlob() {
+    CommitMessageFetcher fetcher = createCommitMessageFetcher();
+    String commitMessage = fetcher.fetchGuarded("ProjectFoo", objectIdBlob);
+
+    assertThat(commitMessage).isEmpty();
+  }
+
+  @Test
+  public void testFetchGuardedTree() {
+    CommitMessageFetcher fetcher = createCommitMessageFetcher();
+    String commitMessage = fetcher.fetchGuarded("ProjectFoo", objectIdTree);
+
+    assertThat(commitMessage).isEmpty();
+  }
+
+  @Test
+  public void testFetchGuardedCommit() {
+    CommitMessageFetcher fetcher = createCommitMessageFetcher();
+    String commitMessage = fetcher.fetchGuarded("ProjectFoo", objectIdCommit);
+
+    assertThat(commitMessage).isEqualTo("CommitMsg\n");
+  }
+
+  @Test
+  public void testFetchGuardedMissing() {
+    CommitMessageFetcher fetcher = createCommitMessageFetcher();
+    String commitMessage = fetcher.fetchGuarded("ProjectFoo", objectIdMissing);
+
+    assertThat(commitMessage).isEmpty();
+
+    assertLogMessageContains(objectIdMissing);
+  }
+
+  @Override
+  public void setUp() throws Exception {
+    super.setUp();
+
+    ObjectLoader objectLoaderBlob = mock(ObjectLoader.class);
+    when(objectLoaderBlob.getCachedBytes(anyInt())).thenReturn(rawBlob);
+    when(objectLoaderBlob.getType()).thenReturn(Constants.OBJ_BLOB);
+
+    ObjectLoader objectLoaderTree = mock(ObjectLoader.class);
+    when(objectLoaderTree.getCachedBytes(anyInt())).thenReturn(rawTree);
+    when(objectLoaderTree.getType()).thenReturn(Constants.OBJ_TREE);
+
+    ObjectLoader objectLoaderCommit = mock(ObjectLoader.class);
+    when(objectLoaderCommit.getCachedBytes(anyInt())).thenReturn(rawCommit);
+    when(objectLoaderCommit.getType()).thenReturn(Constants.OBJ_COMMIT);
+
+    Set<ObjectId> shallowCommits = new HashSet<>();
+    shallowCommits.add(ObjectId.fromString(objectIdCommit));
+
+    ObjectReader objectReader = mock(ObjectReader.class);
+    when(objectReader.getShallowCommits()).thenReturn(shallowCommits);
+    when(objectReader.open(ObjectId.fromString(objectIdBlob))).thenReturn(objectLoaderBlob);
+    when(objectReader.open(ObjectId.fromString(objectIdTree))).thenReturn(objectLoaderTree);
+    when(objectReader.open(ObjectId.fromString(objectIdCommit))).thenReturn(objectLoaderCommit);
+    when(objectReader.open(ObjectId.fromString(objectIdMissing)))
+        .thenThrow(
+            new MissingObjectException(ObjectId.fromString(objectIdMissing), Constants.OBJ_COMMIT));
+
+    repo = mock(Repository.class);
+    when(repo.newObjectReader()).thenReturn(objectReader);
+
+    repoManager = mock(GitRepositoryManager.class);
+    when(repoManager.openRepository(eq(new Project.NameKey("ProjectFoo")))).thenReturn(repo);
+  }
+
+  private CommitMessageFetcher createCommitMessageFetcher() {
+    return new CommitMessageFetcher(repoManager);
+  }
+}