diff --git a/core/hashtables/hashtables.factor b/core/hashtables/hashtables.factor
index 9da1d96ecb..9ed4571288 100644
--- a/core/hashtables/hashtables.factor
+++ b/core/hashtables/hashtables.factor
@@ -188,7 +188,9 @@ M: hashtable assoc-like
 ! magic number is 2^29/phi instead of 2^32/phi
 ! due to max fixnum value on 32-bit machines
 : hash-combine ( hash1 hash2 -- newhash )
-    [ 0x13c6ef37 + ] dip [ 6 shift ] [ -2 shift ] bi + + ; inline
+    [ >fixnum ] bi@ [ 0x13c6ef37 fixnum+fast ] dip
+    [ 6 fixnum-shift-fast ] [ -2 fixnum-shift-fast ] bi
+    fixnum+fast fixnum+fast ; inline
 
 : 2hashcode ( obj1 obj2 -- hash )
     [ hashcode ] bi@ hash-combine ; inline