diff --git a/winsup/cygwin/winsup.h b/winsup/cygwin/winsup.h
index 114678548..c84e72584 100644
--- a/winsup/cygwin/winsup.h
+++ b/winsup/cygwin/winsup.h
@@ -500,7 +500,7 @@ win_env * __stdcall getwinenv (const char *name, const char *posix = NULL);
 void __stdcall update_envptrs ();
 char * __stdcall winenv (const char * const *, int);
 extern char **__cygwin_environ, ***main_environ;
-extern char __stdcall **cur_environ ();
+extern "C" char __stdcall **cur_environ ();
 #define environ (cur_environ ())
 
 /* The title on program start. */