diff --git a/file.c b/file.c
index de7ed5e33b..862f9630df 100644
--- a/file.c
+++ b/file.c
@@ -6504,12 +6504,10 @@ rb_find_file(VALUE path)
     return copy_path_class(tmp, path);
 }
 
-static void
-define_filetest_function(const char *name, VALUE (*func)(ANYARGS), int argc)
-{
-    rb_define_module_function(rb_mFileTest, name, func, argc);
-    rb_define_singleton_method(rb_cFile, name, func, argc);
-}
+#define define_filetest_function(name, func, argc) do {        \
+    rb_define_module_function(rb_mFileTest, name, func, argc); \
+    rb_define_singleton_method(rb_cFile, name, func, argc);    \
+} while(false)
 
 const char ruby_null_device[] =
 #if defined DOSISH