diff --git a/node.h b/node.h
index ad020fe008..c55bbe1afc 100644
--- a/node.h
+++ b/node.h
@@ -378,7 +378,7 @@ typedef unsigned int rb_event_t;
 #define RUBY_EVENT_RAISE    0x80
 #define RUBY_EVENT_ALL      0xff
 
-typedef void (*rb_event_hook_func_t)_((rb_event_t,NODE*,VALUE,ID,VALUE));
+typedef void (*rb_event_hook_func_t) _((rb_event_t,NODE*,VALUE,ID,VALUE));
 void rb_add_event_hook _((rb_event_hook_func_t,rb_event_t));
 int rb_remove_event_hook _((rb_event_hook_func_t));