diff --git a/memcached.h b/memcached.h
index 689a6f59c1..99cf0b5d8e 100644
--- a/memcached.h
+++ b/memcached.h
@@ -77,7 +77,7 @@
 
 /* Slab sizing definitions. */
 #define POWER_SMALLEST 1
-#define POWER_LARGEST  255
+#define POWER_LARGEST  256 /* actual cap is 255 */
 #define CHUNK_ALIGN_BYTES 8
 /* slab class max is a 6-bit number, -1. */
 #define MAX_NUMBER_OF_SLAB_CLASSES (63 + 1)