diff --git a/pkgs/development/libraries/qt-5/modules/qtwebkit.nix b/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
index 4dce9c4e22e..6834b7ce87b 100644
--- a/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
+++ b/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
@@ -31,7 +31,8 @@ qtModule {
   '';
 
   NIX_CFLAGS_COMPILE =
-    optionals flashplayerFix
+    [ "-Wno-expansion-to-defined" ] # with gcc7 this warning blows the log over Hydra's limit
+    ++ optionals flashplayerFix
       [
         ''-DNIXPKGS_LIBGTK2="${getLib gtk2}/lib/libgtk-x11-2.0"''
         ''-DNIXPKGS_LIBGDK2="${getLib gdk_pixbuf}/lib/libgdk-x11-2.0"''