diff --git a/test/compare_sgemm_sbgemm.c b/test/compare_sgemm_sbgemm.c
index 57d416c943..b723b6a3b5 100644
--- a/test/compare_sgemm_sbgemm.c
+++ b/test/compare_sgemm_sbgemm.c
@@ -49,7 +49,7 @@ typedef union
 typedef union
 {
   float v;
-  struct
+  struct __attribute__((packed))
   {
 #if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
     uint32_t s:1;