diff --git a/gerrit-extension-api/BUCK b/gerrit-extension-api/BUCK
index 0c1b6a8f5b..be90e60039 100644
--- a/gerrit-extension-api/BUCK
+++ b/gerrit-extension-api/BUCK
@@ -8,6 +8,7 @@ gwt_module(
     SRC + 'common/InheritableBoolean.java',
     SRC + 'common/ListChangesOption.java',
     SRC + 'common/SubmitType.java',
+    SRC + 'common/Theme.java',
     SRC + 'webui/GerritTopMenu.java',
   ]),
   gwt_xml = SRC + 'Extensions.gwt.xml',
diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/Theme.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/Theme.java
new file mode 100644
index 0000000000..1a665786ab
--- /dev/null
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/Theme.java
@@ -0,0 +1,38 @@
+// Copyright (C) 2014 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.google.gerrit.extensions.common;
+
+public enum Theme {
+  // Light themes
+  DEFAULT,
+  ECLIPSE,
+  ELEGANT,
+  NEAT,
+  // Dark themes
+  MIDNIGHT,
+  NIGHT,
+  TWILIGHT;
+
+  public boolean isDark() {
+    switch (this) {
+      case MIDNIGHT:
+      case NIGHT:
+      case TWILIGHT:
+        return true;
+      default:
+        return false;
+    }
+  }
+}
\ No newline at end of file
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/account/DiffPreferences.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/account/DiffPreferences.java
index 029e7c2aa4..5aa211938e 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/account/DiffPreferences.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/account/DiffPreferences.java
@@ -14,8 +14,8 @@
 
 package com.google.gerrit.client.account;
 
+import com.google.gerrit.extensions.common.Theme;
 import com.google.gerrit.reviewdb.client.AccountDiffPreference;
-import com.google.gerrit.reviewdb.client.AccountDiffPreference.Theme;
 import com.google.gerrit.reviewdb.client.AccountDiffPreference.Whitespace;
 import com.google.gwt.core.client.JavaScriptObject;
 
diff --git a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/PreferencesBox.java b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/PreferencesBox.java
index 9ea5c8d679..f09e8239cd 100644
--- a/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/PreferencesBox.java
+++ b/gerrit-gwtui/src/main/java/com/google/gerrit/client/diff/PreferencesBox.java
@@ -28,8 +28,8 @@ import com.google.gerrit.client.account.DiffPreferences;
 import com.google.gerrit.client.patches.PatchUtil;
 import com.google.gerrit.client.rpc.GerritCallback;
 import com.google.gerrit.client.ui.NpIntTextBox;
+import com.google.gerrit.extensions.common.Theme;
 import com.google.gerrit.reviewdb.client.AccountDiffPreference;
-import com.google.gerrit.reviewdb.client.AccountDiffPreference.Theme;
 import com.google.gerrit.reviewdb.client.AccountDiffPreference.Whitespace;
 import com.google.gerrit.reviewdb.client.Patch.ChangeType;
 import com.google.gwt.core.client.GWT;
diff --git a/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountDiffPreference.java b/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountDiffPreference.java
index 1d7b2f724b..1f1e6cb09d 100644
--- a/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountDiffPreference.java
+++ b/gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/AccountDiffPreference.java
@@ -14,6 +14,7 @@
 
 package com.google.gerrit.reviewdb.client;
 
+import com.google.gerrit.extensions.common.Theme;
 import com.google.gwtorm.client.Column;
 
 /** Diff formatting preferences of an account */
@@ -56,29 +57,6 @@ public class AccountDiffPreference {
     }
   }
 
-  public static enum Theme {
-    // Light themes
-    DEFAULT,
-    ECLIPSE,
-    ELEGANT,
-    NEAT,
-    // Dark themes
-    MIDNIGHT,
-    NIGHT,
-    TWILIGHT;
-
-    public boolean isDark() {
-      switch (this) {
-        case MIDNIGHT:
-        case NIGHT:
-        case TWILIGHT:
-          return true;
-        default:
-          return false;
-      }
-    }
-  }
-
   public static AccountDiffPreference createDefault(Account.Id accountId) {
     AccountDiffPreference p = new AccountDiffPreference(accountId);
     p.setIgnoreWhitespace(Whitespace.IGNORE_NONE);
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/GetDiffPreferences.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/GetDiffPreferences.java
index 7169e91af8..903d388997 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/GetDiffPreferences.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/GetDiffPreferences.java
@@ -14,11 +14,11 @@
 
 package com.google.gerrit.server.account;
 
+import com.google.gerrit.extensions.common.Theme;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.RestReadView;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.AccountDiffPreference;
-import com.google.gerrit.reviewdb.client.AccountDiffPreference.Theme;
 import com.google.gerrit.reviewdb.client.AccountDiffPreference.Whitespace;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.CurrentUser;
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/account/SetDiffPreferences.java b/gerrit-server/src/main/java/com/google/gerrit/server/account/SetDiffPreferences.java
index d922faf08e..7972efa1d1 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/account/SetDiffPreferences.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/account/SetDiffPreferences.java
@@ -14,11 +14,11 @@
 
 package com.google.gerrit.server.account;
 
+import com.google.gerrit.extensions.common.Theme;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.extensions.restapi.RestModifyView;
 import com.google.gerrit.reviewdb.client.Account;
 import com.google.gerrit.reviewdb.client.AccountDiffPreference;
-import com.google.gerrit.reviewdb.client.AccountDiffPreference.Theme;
 import com.google.gerrit.reviewdb.client.AccountDiffPreference.Whitespace;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.CurrentUser;