diff --git a/basis/math/bitwise/bitwise.factor b/basis/math/bitwise/bitwise.factor
index a0d19b49ec..4dc99e47ec 100644
--- a/basis/math/bitwise/bitwise.factor
+++ b/basis/math/bitwise/bitwise.factor
@@ -90,13 +90,13 @@ GENERIC: (bit-count) ( x -- n )
     { fixnum } declare
     [ byte-bit-count ] keep
     [ -8 shift byte-bit-count + ] keep
-    [ -8 shift byte-bit-count + ] keep
-    [ -8 shift byte-bit-count + ] keep
+    [ -16 shift byte-bit-count + ] keep
+    [ -24 shift byte-bit-count + ] keep
     cell 8 = [
-        [ -8 shift byte-bit-count + ] keep
-        [ -8 shift byte-bit-count + ] keep
-        [ -8 shift byte-bit-count + ] keep
-          -8 shift byte-bit-count + >fixnum
+        [ -32 shift byte-bit-count + ] keep
+        [ -40 shift byte-bit-count + ] keep
+        [ -48 shift byte-bit-count + ] keep
+          -56 shift byte-bit-count + >fixnum
     ] [ drop ] if ;
 
 M: fixnum (bit-count)