diff --git a/pkgs/test/macos-sierra-shared/default.nix b/pkgs/test/macos-sierra-shared/default.nix
index ebcf6c62c60..2d52a02affa 100644
--- a/pkgs/test/macos-sierra-shared/default.nix
+++ b/pkgs/test/macos-sierra-shared/default.nix
@@ -32,7 +32,7 @@ let
 
         #include <assert.h>
 
-        ${toString (lib.genList (i: "extern unsigned int asdf_${toString i}(void); ") count)}
+        ${toString (lib.genList (i: "extern \"C\" unsigned int asdf_${toString i}(void); ") count)}
 
         unsigned int (*funs[])(void) = {
           ${toString (lib.genList (i: "asdf_${toString i},") count)}