diff --git a/pkgs/development/libraries/qt-5/modules/qtwebengine.nix b/pkgs/development/libraries/qt-5/modules/qtwebengine.nix
index df9995bc3b9f..7e91cff065dd 100644
--- a/pkgs/development/libraries/qt-5/modules/qtwebengine.nix
+++ b/pkgs/development/libraries/qt-5/modules/qtwebengine.nix
@@ -63,8 +63,9 @@ qtModule {
         src/3rdparty/chromium/gpu/config/gpu_info_collector_linux.cc
     '';
 
+
   preConfigure = ''
-    export MAKEFLAGS=-j$NIX_BUILD_CORES
+    export NINJAFLAGS=-j$NIX_BUILD_CORES
 
     if [ -d "$PWD/tools/qmake" ]; then
         QMAKEPATH="$PWD/tools/qmake''${QMAKEPATH:+:}$QMAKEPATH"