diff --git a/extra/math/binpack/binpack-tests.factor b/extra/math/binpack/binpack-tests.factor
index 06101450fb..d28eff031f 100644
--- a/extra/math/binpack/binpack-tests.factor
+++ b/extra/math/binpack/binpack-tests.factor
@@ -5,18 +5,18 @@ USING: kernel tools.test sequences ;
 
 IN: math.binpack
 
-{ { { } } } [ { } 1 binpack ] unit-test
+{ { V{ } } } [ { } 1 binpack ] unit-test
 
-{ { { 3 } { 2 1 } } } [ { 1 2 3 } 2 binpack ] unit-test
+{ { V{ 3 } V{ 2 1 } } } [ { 1 2 3 } 2 binpack ] unit-test
 
-{ { { 1000 } { 100 60 30 7 } { 70 60 40 23 3 } } }
+{ { V{ 1000 } V{ 100 60 30 7 } V{ 70 60 40 23 3 } } }
 [ { 100 23 40 60 1000 30 60 07 70 03 } 3 binpack ] unit-test
 
 {
     {
-        { "violet" "orange" }
-        { "indigo" "green" }
-        { "yellow" "blue" "red" }
+        V{ "violet" "orange" }
+        V{ "indigo" "green" }
+        V{ "yellow" "blue" "red" }
     }
 } [
     { "red" "orange" "yellow" "green" "blue" "indigo" "violet" }
diff --git a/extra/math/binpack/binpack.factor b/extra/math/binpack/binpack.factor
index e21225d0f9..4c350d8ecb 100644
--- a/extra/math/binpack/binpack.factor
+++ b/extra/math/binpack/binpack.factor
@@ -15,15 +15,14 @@ TUPLE: bin items total ;
 : smallest-bin ( bins -- bin )
     [ total>> ] infimum-by ; inline
 
-: add-to-bin ( item bin -- )
-    [ items>> push ]
-    [ [ second ] dip [ + ] change-total drop ] 2bi ;
+: add-to-bin ( item weight bin -- )
+    [ + ] change-total items>> push ;
 
 :: (binpack) ( alist #bins -- bins )
     alist sort-values <reversed> :> items
     #bins [ <bin> ] replicate :> bins
-    items [ bins smallest-bin add-to-bin ] each
-    bins [ items>> keys ] map ;
+    items [ bins smallest-bin add-to-bin ] assoc-each
+    bins [ items>> ] map ;
 
 PRIVATE>