diff --git a/slirp/slirp.h b/slirp/slirp.h
index 98a2644..c30c19e 100644
--- a/slirp/slirp.h
+++ b/slirp/slirp.h
@@ -294,7 +294,7 @@ void if_start(struct ttys *);
  long gethostid(void);
 #endif
 
-void lprint(const char *, ...);
+void lprint(const char *, ...) __attribute__ ((__format__ (__printf__, 1, 2)));
 
 #ifndef _WIN32
 #include <netdb.h>