diff --git a/m-core.h b/m-core.h
index ba6c7c96..fa9d8098 100644
--- a/m-core.h
+++ b/m-core.h
@@ -655,7 +655,7 @@
 #define M_HASH_CALC(h1,h2)  ((h2) + ((h1) << 6) + ((h1) << 16) - (h1))
 #elif defined(M_USE_DEKHASH)
 #define M_HASH_INIT 0UL /* should be len but not possible with interface */
-#define M_HASH_CALC(h1,h2)  (((h1)<<5)  ^ (h1 >> 27) ^(h2))
+#define M_HASH_CALC(h1,h2)  ( (((h1)<<5) | (h1 >> (CHAR_BIT*sizeof(size_t)-5))) ^(h2))
 #elif defined(M_USE_BPHASH)
 #define M_HASH_INIT 0UL
 #define M_HASH_CALC(h1,h2)  (((h1) << 7) ^ (h2))