diff --git a/signal.c b/signal.c
index 3f462950..89f5fc17 100644
--- a/signal.c
+++ b/signal.c
@@ -85,8 +85,10 @@
 #ifndef _WIN32
 /* Windows wants us to call our signal handlers as __cdecl.  Nobody else
  * expects you to do anything crazy like this. */
+#ifndef __cdecl
 #define __cdecl
 #endif
+#endif
 
 static int evsig_add(struct event_base *, evutil_socket_t, short, short, void *);
 static int evsig_del(struct event_base *, evutil_socket_t, short, short, void *);