diff --git a/pkgs/development/libraries/gtk-sharp/2.0.nix b/pkgs/development/libraries/gtk-sharp/2.0.nix
index 219028d4ab90..1331fcff0e65 100644
--- a/pkgs/development/libraries/gtk-sharp/2.0.nix
+++ b/pkgs/development/libraries/gtk-sharp/2.0.nix
@@ -54,6 +54,10 @@ stdenv.mkDerivation rec {
     ./bootstrap-${lib.versions.majorMinor version}
   '';
 
+  env.NIX_CFLAGS_COMPILE = toString (lib.optionals stdenv.cc.isClang [
+    "-Wno-error=int-conversion"
+  ]);
+
   dontStrip = true;
 
   inherit monoDLLFixer;