diff --git a/core/classes/classes-tests.factor b/core/classes/classes-tests.factor
index f97f088845..3322c3b043 100755
--- a/core/classes/classes-tests.factor
+++ b/core/classes/classes-tests.factor
@@ -22,6 +22,8 @@ H{ } "s" set
 [ number ] [ number object class-and ] unit-test
 [ number ] [ object number class-and ] unit-test
 [ null ] [ slice reversed class-and ] unit-test
+[ null ] [ general-t \ f class-and ] unit-test
+[ object ] [ general-t \ f class-or ] unit-test
 
 TUPLE: first-one ;
 TUPLE: second-one ;
diff --git a/core/classes/classes.factor b/core/classes/classes.factor
index ad2920e594..e47dbd20e5 100755
--- a/core/classes/classes.factor
+++ b/core/classes/classes.factor
@@ -127,12 +127,14 @@ DEFER: (class<)
 : (class-or) ( class class -- class )
     [ flatten-class ] 2apply class-or-fixup lookup-tuple-union ;
 
-: class-and-fixup ( set set -- set )
-    2dup [ tuple swap key? ] either?
-    [ 2drop H{ { tuple tuple } } ] [ intersect ] if ;
-
 : (class-and) ( class class -- class )
-    [ flatten-class ] 2apply class-and-fixup lookup-tuple-union ;
+    2dup [ tuple swap class< ] either? [
+        [ flatten-builtin-class ] 2apply
+        intersect lookup-union
+    ] [
+        [ flatten-class ] 2apply
+        intersect lookup-tuple-union
+    ] if ;
 
 : tuple-class-and ( class1 class2 -- class )
     dupd eq? [ drop null ] unless ;
diff --git a/core/inference/known-words/known-words.factor b/core/inference/known-words/known-words.factor
index 235c2924bb..08fb56ced7 100755
--- a/core/inference/known-words/known-words.factor
+++ b/core/inference/known-words/known-words.factor
@@ -354,7 +354,7 @@ M: object infer-call
 
 \ setenv { object fixnum } { } <effect> set-primitive-effect
 
-\ (stat) { string } { object object object object } <effect> set-primitive-effect
+\ exists? { string } { object } <effect> set-primitive-effect
 
 \ (directory) { string } { array } <effect> set-primitive-effect