diff --git a/omaha_request_params.h b/omaha_request_params.h
index b6b6f04..90cbc6e 100644
--- a/omaha_request_params.h
+++ b/omaha_request_params.h
@@ -206,7 +206,8 @@
   // numerous edge cases around ensuring the powerwash happens as intended in
   // all such cases.
   virtual bool SetTargetChannel(const std::string& channel,
-                                bool is_powerwash_allowed);
+                                bool is_powerwash_allowed,
+                                std::string* error_message);
 
   // Updates the download channel for this particular attempt from the current
   // value of target channel.  This method takes a "snapshot" of the current