diff --git a/extra/math/extras/extras-tests.factor b/extra/math/extras/extras-tests.factor
index 363192896f..a815283f7d 100644
--- a/extra/math/extras/extras-tests.factor
+++ b/extra/math/extras/extras-tests.factor
@@ -130,7 +130,7 @@ IN: math.extras.test
 { 10 } [ 12 5 round-to-step ] unit-test
 { 15 } [ 13 5 round-to-step ] unit-test
 
-{ 0b101 } [ 0b11 next-permutation-bits ] unit-test
+{ 0b101 } [ 0b011 next-permutation-bits ] unit-test
 { 0b110 } [ 0b101 next-permutation-bits ] unit-test
 
 {
diff --git a/extra/math/extras/extras.factor b/extra/math/extras/extras.factor
index 5cb45d06c9..6888226e15 100644
--- a/extra/math/extras/extras.factor
+++ b/extra/math/extras/extras.factor
@@ -261,7 +261,7 @@ M: float round-to-even
 
 : next-permutation-bits ( v -- w )
     [ dup 1 - bitor 1 + dup ] keep
-    [ dup neg bitand ] bi@ / -1 shift 1 - bitor ;
+    [ dup neg bitand ] bi@ /i -1 shift 1 - bitor ;
 
 : permutation-bits ( bit-count bits -- seq )
     [ on-bits dup '[ dup _ >= ] ]