diff --git a/src/redis.h b/src/redis.h
index b049dbee..2cf96028 100644
--- a/src/redis.h
+++ b/src/redis.h
@@ -626,11 +626,12 @@ typedef struct redisOpArray {
 
 struct clusterState;
 
+/* AIX defines hz to __hz, we don't use this define and in order to allow
+ * Redis build on AIX we need to undef it. */
 #ifdef _AIX
 #undef hz
 #endif
 
-
 struct redisServer {
     /* General */
     pid_t pid;                  /* Main process pid. */