diff --git a/pkgs/development/libraries/kde-frameworks/kinit/default.nix b/pkgs/development/libraries/kde-frameworks/kinit/default.nix
index b8b0d74acad0..533af32e64bb 100644
--- a/pkgs/development/libraries/kde-frameworks/kinit/default.nix
+++ b/pkgs/development/libraries/kde-frameworks/kinit/default.nix
@@ -42,13 +42,15 @@ mkDerivation {
     ./0003-kdeinit-extra-libs.patch
     ./0004-start_kdeinit-environ-hard-limit.patch
   ];
-  CXXFLAGS = [
-    ''-DNIXPKGS_KF5_KIOCORE=\"${getLib kio}/lib/libKF5KIOCore.so.5\"''
-    ''-DNIXPKGS_KF5_PARTS=\"${getLib kparts}/lib/libKF5Parts.so.5\"''
-  ]
-  ++ lib.optionals stdenv.hostPlatform.isLinux [
-    ''-DNIXPKGS_KF5_PLASMA=\"${getLib plasma-framework}/lib/libKF5Plasma.so.5\"''
-  ];
+  env.CXXFLAGS = toString (
+    [
+      ''-DNIXPKGS_KF5_KIOCORE=\"${getLib kio}/lib/libKF5KIOCore.so.5\"''
+      ''-DNIXPKGS_KF5_PARTS=\"${getLib kparts}/lib/libKF5Parts.so.5\"''
+    ]
+    ++ lib.optionals stdenv.hostPlatform.isLinux [
+      ''-DNIXPKGS_KF5_PLASMA=\"${getLib plasma-framework}/lib/libKF5Plasma.so.5\"''
+    ]
+  );
   setupHook = writeScript "setup-hook.sh" ''
     kinitFixupOutputHook() {
         if [ $prefix != ''${!outputBin} ] && [ -d $prefix/lib ]; then