diff --git a/src/lxc/utils.h b/src/lxc/utils.h
index 0d63bb699..3d1ecee4a 100644
--- a/src/lxc/utils.h
+++ b/src/lxc/utils.h
@@ -35,6 +35,10 @@
 
 #include "initutils.h"
 
+/* Useful macros */
+/* Maximum number for 64 bit integer is a string with 21 digits: 2^64 - 1 = 21 */
+#define __LXC_NUMSTRLEN 21
+
 /* returns 1 on success, 0 if there were any failures */
 extern int lxc_rmdir_onedev(char *path, const char *exclude);
 extern int get_u16(unsigned short *val, const char *arg, int base);