diff --git a/pkgs/kde/lib/mk-kde-derivation.nix b/pkgs/kde/lib/mk-kde-derivation.nix
index 80508eebb7d4..042c7531f07e 100644
--- a/pkgs/kde/lib/mk-kde-derivation.nix
+++ b/pkgs/kde/lib/mk-kde-derivation.nix
@@ -100,6 +100,8 @@ in
       cmakeFlags = ["-DQT_MAJOR_VERSION=6"] ++ extraCmakeFlags;
 
       separateDebugInfo = true;
+
+      env.LANG = "C.UTF-8";
     };
 
     cleanArgs = builtins.removeAttrs args [