diff --git a/library/generic/generic.factor b/library/generic/generic.factor
index bf68267652..c4e376498d 100644
--- a/library/generic/generic.factor
+++ b/library/generic/generic.factor
@@ -162,6 +162,9 @@ SYMBOL: object
 : type-union ( list list -- list )
     append prune [ > ] sort ;
 
+: type-intersection ( list list -- list )
+    intersection [ > ] sort ;
+
 : class-or ( class class -- class )
     #! Return a class that both classes are subclasses of.
     swap builtin-supertypes
@@ -173,7 +176,7 @@ SYMBOL: object
     #! error if this is impossible.
     over builtin-supertypes
     over builtin-supertypes
-    intersection dup [
+    type-intersection dup [
         nip nip classes get hash [ object ] unless*
     ] [
         drop [
@@ -187,4 +190,4 @@ SYMBOL: object
     dup builtin-supertypes [ > ] sort
     classes get set-hash ;
 
-global [ <namespace> classes set ] bind
+global [ classes get [ <namespace> classes set ] unless ] bind
diff --git a/library/inference/words.factor b/library/inference/words.factor
index f5970a0c6c..eef233f211 100644
--- a/library/inference/words.factor
+++ b/library/inference/words.factor
@@ -37,7 +37,6 @@ USE: strings
 USE: vectors
 USE: words
 USE: hashtables
-USE: prettyprint
 
 : with-dataflow ( param op [ in | out ] quot -- )
     #! Take input parameters, execute quotation, take output
diff --git a/library/test/generic.factor b/library/test/generic.factor
index d84b8659fe..dc119ab099 100644
--- a/library/test/generic.factor
+++ b/library/test/generic.factor
@@ -136,3 +136,5 @@ M: very-funny gooey sq ;
 [ integer ] [ fixnum bignum class-or ] unit-test
 [ integer ] [ fixnum integer class-or ] unit-test
 [ rational ] [ ratio integer class-or ] unit-test
+[ number ] [ number object class-and ] unit-test
+[ number ] [ object number class-and ] unit-test
diff --git a/library/test/inference.factor b/library/test/inference.factor
index 027ead5342..29bb6eb0b1 100644
--- a/library/test/inference.factor
+++ b/library/test/inference.factor
@@ -203,3 +203,4 @@ SYMBOL: sym-test
 [ [ [ cons ] [ cons ] ] ] [ [ uncons cons ] infer ] unit-test
 [ [ [ object ] [ object ] ] ] [ [ dup [ car ] when ] infer ] unit-test
 [ [ [ vector ] [ vector ] ] ] [ [ vector-clone ] infer ] unit-test
+[ [ [ number ] [ number ] ] ] [ [ dup + ] infer ] unit-test