diff --git a/common/mock_prefs.h b/common/mock_prefs.h
index 62417a8..c91664e 100644
--- a/common/mock_prefs.h
+++ b/common/mock_prefs.h
@@ -41,6 +41,9 @@
 
   MOCK_CONST_METHOD1(Exists, bool(const std::string& key));
   MOCK_METHOD1(Delete, bool(const std::string& key));
+  MOCK_METHOD2(Delete,
+               bool(const std::string& key,
+                    const std::vector<std::string>& nss));
 
   MOCK_CONST_METHOD2(GetSubKeys,
                      bool(const std::string&, std::vector<std::string>*));