diff --git a/basis/stack-checker/row-polymorphism/row-polymorphism.factor b/basis/stack-checker/row-polymorphism/row-polymorphism.factor
index 76879a3950..29ee63bf33 100644
--- a/basis/stack-checker/row-polymorphism/row-polymorphism.factor
+++ b/basis/stack-checker/row-polymorphism/row-polymorphism.factor
@@ -37,7 +37,7 @@ IN: stack-checker.row-polymorphism
         [ variable vars at -     ]
         [ variable vars set-at 0 ] if
         t
-    ] [ dup zero? ] if ;
+    ] [ dup 0 <= ] if ;
 
 : adjust-variable ( diff var vars -- )
     pick 0 >=
diff --git a/basis/stack-checker/stack-checker-tests.factor b/basis/stack-checker/stack-checker-tests.factor
index e537a530d2..ce2c03264b 100644
--- a/basis/stack-checker/stack-checker-tests.factor
+++ b/basis/stack-checker/stack-checker-tests.factor
@@ -431,9 +431,18 @@ DEFER: eee'
 
 : strict-each ( seq quot: ( x -- ) -- )
     each ; inline
+: strict-map ( seq quot: ( x -- x' ) -- seq' )
+    map ; inline
+: strict-2map ( xs ys quot: ( x y -- z ) -- zs )
+    2map ; inline
 
 { 1 0 } [ [ drop ] strict-each ] must-infer-as
+{ 1 1 } [ [ 1 + ] strict-map ] must-infer-as
+{ 1 1 } [ [  ] strict-map ] must-infer-as
+{ 2 1 } [ [ + ] strict-2map ] must-infer-as
+{ 2 1 } [ [ drop ] strict-2map ] must-infer-as
 [ [ [ append ] strict-each ] infer ] [ unbalanced-branches-error? ] must-fail-with
+[ [ [ 1 + ] strict-2map ] infer ] [ unbalanced-branches-error? ] must-fail-with
 
 ! ensure that polymorphic checking works on recursive combinators
 FROM: splitting.private => split, ;