diff --git a/core/assocs/assocs.factor b/core/assocs/assocs.factor
index 58a2a29eb1..0508d2e569 100644
--- a/core/assocs/assocs.factor
+++ b/core/assocs/assocs.factor
@@ -117,7 +117,7 @@ M: assoc assoc-clone-like ( assoc exemplar -- newassoc )
     [ at* [ = ] [ 2drop f ] if ] with-assoc assoc-all? ;
 
 : assoc= ( assoc1 assoc2 -- ? )
-    [ assoc-subset? ] [ swap assoc-subset? ] 2bi and ;
+    2dup [ assoc-size ] bi@ eq? [ assoc-subset? ] [ 2drop f ] if ;
 
 : assoc-hashcode ( n assoc -- code )
     >alist hashcode* ;
diff --git a/core/hashtables/hashtables.factor b/core/hashtables/hashtables.factor
index be5aa97634..e7acf12454 100644
--- a/core/hashtables/hashtables.factor
+++ b/core/hashtables/hashtables.factor
@@ -151,10 +151,7 @@ M: hashtable clone
     (clone) [ clone ] change-array ; inline
 
 M: hashtable equal?
-    over hashtable? [
-        2dup [ assoc-size ] bi@ eq?
-        [ assoc= ] [ 2drop f ] if
-    ] [ 2drop f ] if ;
+    over hashtable? [ assoc= ] [ 2drop f ] if ;
 
 ! Default method
 M: assoc new-assoc drop <hashtable> ; inline
diff --git a/core/sets/sets-tests.factor b/core/sets/sets-tests.factor
index 899a43af4f..df6185671c 100644
--- a/core/sets/sets-tests.factor
+++ b/core/sets/sets-tests.factor
@@ -5,10 +5,14 @@ IN: sets.tests
 
 [ { } ] [ { } { } intersect ] unit-test
 [ { 2 3 } ] [ { 1 2 3 } { 2 3 4 } intersect ] unit-test
+[ { 2 3 } ] [ { 1 2 3 } { 2 3 4 5 } intersect ] unit-test
+[ { 2 3 4 } ] [ { 1 2 3 4 } { 2 3 4 } intersect ] unit-test
 [ { 2 3 } ] [ { 1 2 2 3 } { 2 3 3 4 } intersect ] unit-test
 
 [ { } ] [ { } { } diff ] unit-test
 [ { 1 } ] [ { 1 2 3 } { 2 3 4 } diff ] unit-test
+[ { 1 } ] [ { 1 2 3 } { 2 3 4 5 } diff ] unit-test
+[ { 1 } ] [ { 1 2 3 4 } { 2 3 4 } diff ] unit-test
 [ { 1 } ] [ { 1 1 2 3 } { 2 3 4 4 } diff ] unit-test
 
 [ { } ] [ { } { } within ] unit-test
diff --git a/core/sets/sets.factor b/core/sets/sets.factor
index ae15908e4c..06f6e04655 100644
--- a/core/sets/sets.factor
+++ b/core/sets/sets.factor
@@ -46,22 +46,25 @@ M: set union
 : sequence/tester ( set1 set2 -- set1' quot )
     [ members ] [ tester ] bi* ; inline
 
+: small/large ( set1 set2 -- set1' set2' )
+    2dup [ cardinality ] bi@ > [ swap ] when ;
+
 PRIVATE>
 
 M: set intersect
-    [ sequence/tester filter ] keep set-like ;
+    [ small/large sequence/tester filter ] keep set-like ;
 
 M: set diff
     [ sequence/tester [ not ] compose filter ] keep set-like ;
 
 M: set intersects?
-    sequence/tester any? ;
+    small/large sequence/tester any? ;
 
 M: set subset?
-    sequence/tester all? ;
+    small/large sequence/tester all? ;
 
 M: set set=
-    2dup subset? [ swap subset? ] [ 2drop f ] if ;
+    2dup [ cardinality ] bi@ eq? [ subset? ] [ 2drop f ] if ;
 
 M: set fast-set ;