diff --git a/pkgs/development/libraries/qt-5/modules/qtwebkit.nix b/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
index d65449023b34..78404ddffa87 100644
--- a/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
+++ b/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
@@ -51,8 +51,12 @@ qtModule {
   '';
 
   NIX_CFLAGS_COMPILE =
-    # with gcc7 this warning blows the log over Hydra's limit
-    [ "-Wno-expansion-to-defined" ]
+    [
+      # with gcc7 this warning blows the log over Hydra's limit
+      "-Wno-expansion-to-defined"
+      # with gcc8, -Wclass-memaccess became part of -Wall and this too exceeds the logging limit
+      "-Wno-class-memaccess"
+    ]
     # with clang this warning blows the log over Hydra's limit
     ++ optional stdenv.isDarwin "-Wno-inconsistent-missing-override"
     ++ optionals flashplayerFix