diff --git a/src/main/java/com/googlesource/gerrit/plugins/cookbook/CommitValidator.java b/src/main/java/com/googlesource/gerrit/plugins/cookbook/CommitValidator.java
new file mode 100644
index 0000000..9bc6f5d
--- /dev/null
+++ b/src/main/java/com/googlesource/gerrit/plugins/cookbook/CommitValidator.java
@@ -0,0 +1,38 @@
+// Copyright (C) 2015 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.cookbook;
+
+import com.google.common.collect.ImmutableList;
+import com.google.gerrit.server.events.CommitReceivedEvent;
+import com.google.gerrit.server.git.validators.CommitValidationException;
+import com.google.gerrit.server.git.validators.CommitValidationListener;
+import com.google.gerrit.server.git.validators.CommitValidationMessage;
+
+import java.util.List;
+
+public class CommitValidator implements CommitValidationListener {
+  @Override
+  public List<CommitValidationMessage> onCommitReceived(
+      CommitReceivedEvent receiveEvent) throws CommitValidationException {
+    if ("plugins/cookbook".equals(receiveEvent.project.getName()) &&
+        !receiveEvent.commit.getShortMessage().startsWith("Cookbook: ")) {
+      CommitValidationMessage m = new CommitValidationMessage(
+          "Subject should begin with 'Cookbook: '", true);
+      throw new CommitValidationException(
+          "Invalid commit message", ImmutableList.of(m));
+    }
+    return ImmutableList.of();
+  }
+}
diff --git a/src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java b/src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java
index 2d09990..814c295 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/cookbook/Module.java
@@ -29,6 +29,7 @@
 import com.google.gerrit.extensions.webui.ProjectWebLink;
 import com.google.gerrit.extensions.webui.TopMenu;
 import com.google.gerrit.server.config.ProjectConfigEntry;
+import com.google.gerrit.server.git.validators.CommitValidationListener;
 import com.google.gerrit.server.git.validators.MergeValidationListener;
 import com.google.gerrit.server.git.validators.UploadValidationListener;
 import com.google.gerrit.server.plugins.ServerPluginProvider;
@@ -66,6 +67,8 @@
         .to(HashtagValidator.class);
     DynamicSet.bind(binder(), NewProjectCreatedListener.class)
         .to(ProjectCreatedListener.class);
+    DynamicSet.bind(binder(), CommitValidationListener.class)
+        .to(CommitValidator.class);
     configurePluginParameters();
   }