diff --git a/include/asterisk/utils.h b/include/asterisk/utils.h
index cb96dc1ff3..4b1a7f4173 100644
--- a/include/asterisk/utils.h
+++ b/include/asterisk/utils.h
@@ -474,7 +474,7 @@ char * attribute_malloc _ast_strndup(const char *str, size_t len, const char *fi
 #define ast_asprintf(ret, fmt, ...) \
 	_ast_asprintf((ret), __FILE__, __LINE__, __PRETTY_FUNCTION__, fmt, __VA_ARGS__)
 
-int _ast_asprintf(char **ret, const char *file, int lineno, const char *func, const char *fmt, ...);
+int _ast_asprintf(char **ret, const char *file, int lineno, const char *func, const char *fmt, ...) __attribute__ ((format (printf, 5, 6)));
 
 /*!
  * \brief A wrapper for vasprintf()