diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/ReviewerApi.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/ReviewerApi.java
index 11b670da43..5571726794 100644
--- a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/ReviewerApi.java
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/changes/ReviewerApi.java
@@ -14,6 +14,7 @@
 
 package com.google.gerrit.extensions.api.changes;
 
+import com.google.gerrit.extensions.restapi.NotImplementedException;
 import com.google.gerrit.extensions.restapi.RestApiException;
 
 import java.util.Map;
@@ -22,4 +23,20 @@ public interface ReviewerApi {
 
   Map<String, Short> votes() throws RestApiException;
   void deleteVote(String label) throws RestApiException;
+
+  /**
+   * A default implementation which allows source compatibility
+   * when adding new methods to the interface.
+   **/
+  class NotImplemented implements ReviewerApi {
+    @Override
+    public Map<String, Short> votes() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void deleteVote(String label) throws RestApiException {
+      throw new NotImplementedException();
+    }
+  }
 }
diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/groups/GroupApi.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/groups/GroupApi.java
index f5a89c05c6..d3f4463cca 100644
--- a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/groups/GroupApi.java
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/groups/GroupApi.java
@@ -18,6 +18,7 @@ import com.google.gerrit.extensions.common.AccountInfo;
 import com.google.gerrit.extensions.common.GroupAuditEventInfo;
 import com.google.gerrit.extensions.common.GroupInfo;
 import com.google.gerrit.extensions.common.GroupOptionsInfo;
+import com.google.gerrit.extensions.restapi.NotImplementedException;
 import com.google.gerrit.extensions.restapi.RestApiException;
 
 import java.util.List;
@@ -141,4 +142,102 @@ public interface GroupApi {
    * @throws RestApiException
    */
   List<? extends GroupAuditEventInfo> auditLog() throws RestApiException;
+
+  /**
+   * A default implementation which allows source compatibility
+   * when adding new methods to the interface.
+   **/
+  class NotImplemented implements GroupApi {
+    @Override
+    public GroupInfo get() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public GroupInfo detail() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public String name() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void name(String name) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public GroupInfo owner() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void owner(String owner) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public String description() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void description(String description) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public GroupOptionsInfo options() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void options(GroupOptionsInfo options) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public List<AccountInfo> members() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public List<AccountInfo> members(boolean recursive)
+        throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void addMembers(String... members) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void removeMembers(String... members) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public List<GroupInfo> includedGroups() throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void addGroups(String... groups) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public void removeGroups(String... groups) throws RestApiException {
+      throw new NotImplementedException();
+    }
+
+    @Override
+    public List<? extends GroupAuditEventInfo> auditLog()
+        throws RestApiException {
+      throw new NotImplementedException();
+    }
+  }
 }
diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/groups/Groups.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/groups/Groups.java
index 6b4f5f3f58..608abd6687 100644
--- a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/groups/Groups.java
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/api/groups/Groups.java
@@ -16,6 +16,7 @@ package com.google.gerrit.extensions.api.groups;
 
 import com.google.gerrit.extensions.client.ListGroupsOption;
 import com.google.gerrit.extensions.common.GroupInfo;
+import com.google.gerrit.extensions.restapi.NotImplementedException;
 import com.google.gerrit.extensions.restapi.RestApiException;
 
 import java.util.ArrayList;
@@ -173,5 +174,31 @@ public interface Groups {
     public String getSuggest() {
       return suggest;
     }
+
+    /**
+     * A default implementation which allows source compatibility
+     * when adding new methods to the interface.
+     **/
+    class NotImplemented implements Groups {
+      @Override
+      public GroupApi id(String id) throws RestApiException {
+        throw new NotImplementedException();
+      }
+
+      @Override
+      public GroupApi create(String name) throws RestApiException {
+        throw new NotImplementedException();
+      }
+
+      @Override
+      public GroupApi create(GroupInput input) throws RestApiException {
+        throw new NotImplementedException();
+      }
+
+      @Override
+      public ListRequest list() {
+        throw new NotImplementedException();
+      }
+    }
   }
 }