diff --git a/pkgs/development/libraries/qt-5/modules/qtwebengine.nix b/pkgs/development/libraries/qt-5/modules/qtwebengine.nix
index c96aef3f4da..df444eee2eb 100644
--- a/pkgs/development/libraries/qt-5/modules/qtwebengine.nix
+++ b/pkgs/development/libraries/qt-5/modules/qtwebengine.nix
@@ -103,7 +103,7 @@ EOF
       --replace 'libs = [ "sandbox" ]' 'libs = [ "/usr/lib/libsandbox.1.dylib" ]'
     '');
 
-  NIX_CFLAGS_COMPILE = [
+  NIX_CFLAGS_COMPILE = lib.optionals stdenv.cc.isGNU [
     # with gcc8, -Wclass-memaccess became part of -Wall and this exceeds the logging limit
     "-Wno-class-memaccess"
   ] ++ lib.optionals (stdenv.hostPlatform.platform.gcc.arch or "" == "sandybridge") [
diff --git a/pkgs/development/libraries/qt-5/modules/qtwebkit.nix b/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
index 78404ddffa8..542afdd55da 100644
--- a/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
+++ b/pkgs/development/libraries/qt-5/modules/qtwebkit.nix
@@ -50,13 +50,12 @@ qtModule {
     export qmakeFlags="$qmakeFlags CONFIG+=silent"
   '';
 
-  NIX_CFLAGS_COMPILE =
-    [
+  NIX_CFLAGS_COMPILE = [
       # 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 gcc8, -Wclass-memaccess became part of -Wall and this too exceeds the logging limit
+    ++ optional stdenv.cc.isGNU "-Wno-class-memaccess"
     # with clang this warning blows the log over Hydra's limit
     ++ optional stdenv.isDarwin "-Wno-inconsistent-missing-override"
     ++ optionals flashplayerFix