diff --git a/lib/easyif.h b/lib/easyif.h
index eed160577..043ff437d 100644
--- a/lib/easyif.h
+++ b/lib/easyif.h
@@ -26,7 +26,7 @@
  * Prototypes for library-wide functions provided by easy.c
  */
 #ifdef CURLDEBUG
-CURLcode curl_easy_perform_ev(CURL *easy);
+CURL_EXTERN CURLcode curl_easy_perform_ev(CURL *easy);
 #endif
 
 #endif /* HEADER_CURL_EASYIF_H */