diff --git a/pkgs/by-name/qt/qtwebapp/package.nix b/pkgs/by-name/qt/qtwebapp/package.nix
index 52b17e7c0403..b5a059d15777 100644
--- a/pkgs/by-name/qt/qtwebapp/package.nix
+++ b/pkgs/by-name/qt/qtwebapp/package.nix
@@ -27,6 +27,11 @@ stdenv.mkDerivation (finalAttrs: {
       INSTALLS += target
     }
     EOF
+  ''
+  + lib.optionalString stdenv.hostPlatform.isDarwin ''
+    substituteInPlace QtWebApp.pro \
+      --replace-fail "QMAKE_CXXFLAGS += -std=c++11" "QMAKE_CXXFLAGS += -std=c++20" \
+      --replace-fail "CONFIG += c++11" "CONFIG += c++20"
   '';
 
   nativeBuildInputs = [