diff --git a/client_library/client_impl.h b/client_library/client_impl.h
index 8c11ac2..4886692 100644
--- a/client_library/client_impl.h
+++ b/client_library/client_impl.h
@@ -56,7 +56,7 @@
 
   void RebootIfNeeded() override;
 
-  bool GetPrevVersion(std::string* prev_version);
+  bool GetPrevVersion(std::string* prev_version) override;
 
   bool ResetStatus() override;