diff --git a/configure.ac b/configure.ac
index f30187fbb..91f4f88cb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -149,9 +149,11 @@ AC_CONFIG_HEADERS(config.h)
 AH_BOTTOM([#if __GNUC__ >= 3
 #define __warn_unused __attribute__ ((warn_unused_result))
 #define __sentinel __attribute__ ((sentinel))
+#define __packed __attribute__ ((packed))
 #else
 #define __warn_unused
 #define __sentinel
+#define __packed
 #endif])