diff --git a/lib/strerror.c b/lib/strerror.c
index 32ece136eb50a5f8013299286c4d1fb9c982f6c0..a6f25d0c470ffa604bd5eb6155ac2b541ee57ff2 100644
--- a/lib/strerror.c
+++ b/lib/strerror.c
@@ -488,7 +488,9 @@ get_winsock_error (int err, char *buf, size_t len)
 }
 #endif   /* WIN32 && !__CYGWIN__ */
 
+#ifndef WIN32
 extern int sys_nerr;
+#endif
 
 /*
  * Our thread-safe and smart strerror() replacement.