diff --git a/include/my_global.h b/include/my_global.h
index b7b200fdcf4..5e31a66e5e3 100644
--- a/include/my_global.h
+++ b/include/my_global.h
@@ -828,7 +828,12 @@ error "Neither int or long is of 4 bytes width"
 typedef unsigned long	ulong;		  /* Short for unsigned long */
 #endif
 #ifndef longlong_defined
-#if defined(HAVE_LONG_LONG) && SIZEOF_LONG != 8
+/* 
+  Using [unsigned] long long is preferable as [u]longlong because we use 
+  [unsigned] long long unconditionally in many places, 
+  for example in constants with [U]LL suffix.
+*/
+#if defined(HAVE_LONG_LONG) && SIZEOF_LONG_LONG == 8
 typedef unsigned long long int ulonglong; /* ulong or unsigned long long */
 typedef long long int	longlong;
 #else