diff --git a/ext/standard/file.c b/ext/standard/file.c
index 66fb2068b50..dc8e2276f83 100644
--- a/ext/standard/file.c
+++ b/ext/standard/file.c
@@ -75,7 +75,7 @@
 #endif
 
 #if MISSING_FCLOSE_DECL
-extern int fclose();
+extern int fclose(FILE *);
 #endif
 
 #ifdef HAVE_SYS_MMAN_H