diff --git a/collects/tests/typed-scheme/succeed/logic.ss b/collects/tests/typed-scheme/succeed/logic.ss
index 34f3fd0a..c21abe72 100644
--- a/collects/tests/typed-scheme/succeed/logic.ss
+++ b/collects/tests/typed-scheme/succeed/logic.ss
@@ -2,7 +2,6 @@
 #lang typed-scheme
 
 (: f ((U Number #f) (cons Any Any) -> Number))
-
 (define (f x y)
  (cond
    [(and (number? x) (number? (car y))) (+ x (car y))]
@@ -11,6 +10,5 @@
    [else 0]))
 
 (: bool-to-0-or-1 (Boolean -> Number))
-
 (define (bool-to-0-or-1 b)
  (if b 1 0))
\ No newline at end of file
diff --git a/collects/tests/typed-scheme/unit-tests/subtype-tests.ss b/collects/tests/typed-scheme/unit-tests/subtype-tests.ss
index c84dcce5..bb3be770 100644
--- a/collects/tests/typed-scheme/unit-tests/subtype-tests.ss
+++ b/collects/tests/typed-scheme/unit-tests/subtype-tests.ss
@@ -126,7 +126,7 @@
    ;; polymorphic function types should be subtypes of the function top
    [(-poly (a) (a . -> . a)) top-func]   
 
-   [(cl->* (-Number . -> . -String) (-Boolean . -> . -String)) ((Un -Number -Boolean) . -> . -String)]
+   [(cl->* (-Number . -> . -String) (-Boolean . -> . -String)) ((Un -Boolean -Number) . -> . -String)]
    ))
 
 (define-go 
diff --git a/collects/typed-scheme/rep/filter-rep.ss b/collects/typed-scheme/rep/filter-rep.ss
index 3c66be2a..56c0f41a 100644
--- a/collects/typed-scheme/rep/filter-rep.ss
+++ b/collects/typed-scheme/rep/filter-rep.ss
@@ -32,7 +32,7 @@
   [#:fold-rhs (*NotTypeFilter (type-rec-id t) (map pathelem-rec-id p) v)])
 
 ;; implication
-(df ImpFilter ([a (listof Filter/c)] [c (listof Filter/c)])
+(df ImpFilter ([a (non-empty-listof Filter/c)] [c (non-empty-listof Filter/c)])
     [#:frees (combine-frees (map free-vars* (append a c)))
 	     (combine-frees (map free-idxs* (append a c)))])
 
@@ -70,8 +70,8 @@
   [#:fold-rhs (*LNotTypeFilter (type-rec-id t) (map pathelem-rec-id p) idx)])
 
 ;; implication
-(df LImpFilter ([a (listof LatentFilter/c)] [c (listof LatentFilter/c)])
-    #;[#:frees (combine-frees (map free-vars* (append a c)))
+(df LImpFilter ([a (non-empty-listof LatentFilter/c)] [c (non-empty-listof LatentFilter/c)])
+    [#:frees (combine-frees (map free-vars* (append a c)))
 	     (combine-frees (map free-idxs* (append a c)))])
 
 
diff --git a/collects/typed-scheme/typecheck/tc-metafunctions.ss b/collects/typed-scheme/typecheck/tc-metafunctions.ss
index 3d98e766..096f7a14 100644
--- a/collects/typed-scheme/typecheck/tc-metafunctions.ss
+++ b/collects/typed-scheme/typecheck/tc-metafunctions.ss
@@ -146,11 +146,12 @@
     [((FilterSet: f1+ f1-) (T-FS:) (FilterSet: f3+ f3-)) (mk (combine null (append f1- f3-)))]
     ;; and
     [((FilterSet: f1+ f1-) (FilterSet: f2+ f2-) (F-FS:)) 
-     (mk (combine (append f1+ f2+)
-		  #;null		  
-		  (append (for/list ([f f1-])
+     (mk (combine (append f1+ f2+)		  
+                  (append (for/list ([f f1-]
+                                     #:when (not (null? f2+)))
 			    (make-ImpFilter f2+ (list f)))
-			  (for/list ([f f2-])
+			  (for/list ([f f2-]
+                                     #:when (not (null? f1+)))
 			    (make-ImpFilter f1+ (list f))))))]
     [(f f* f*) (mk f*)]
     [(_ _ _)
diff --git a/collects/typed-scheme/types/abbrev.ss b/collects/typed-scheme/types/abbrev.ss
index 04559f03..8d141416 100644
--- a/collects/typed-scheme/types/abbrev.ss
+++ b/collects/typed-scheme/types/abbrev.ss
@@ -261,7 +261,6 @@
 (define true-filter (-FS (list) (list (make-Bot))))
 (define false-filter (-FS (list (make-Bot)) (list)))
 
-
 (define (opt-fn args opt-args result)
   (apply cl->* (for/list ([i (in-range (add1 (length opt-args)))])                         
                  (make-Function (list (make-arr* (append args (take opt-args i)) result))))))
diff --git a/collects/typed-scheme/types/printer.ss b/collects/typed-scheme/types/printer.ss
index 33d6602b..beb0cad5 100644
--- a/collects/typed-scheme/types/printer.ss
+++ b/collects/typed-scheme/types/printer.ss
@@ -45,7 +45,8 @@
                            (fp")")]
     [(LNotTypeFilter: type path idx) (fp "(! ~a @ ~a ~a)" type path idx)]
     [(LTypeFilter: type path idx) (fp "(~a @ ~a ~a)" type path idx)]
-    [(LBot:) (fp "LBot")]))
+    [(LBot:) (fp "LBot")]
+    [(LImpFilter: a c) (fp "(LImpFilter ~a ~a)" a c)]))
 
 (define (print-filter c port write?)
   (define (fp . args) (apply fprintf port args))
@@ -57,7 +58,8 @@
     [(NoFilter:) (fp "-")]
     [(NotTypeFilter: type path id) (fp "(! ~a @ ~a ~a)" type path (syntax-e id))]
     [(TypeFilter: type path id) (fp "(~a @ ~a ~a)" type path (syntax-e id))]
-    [(Bot:) (fp "Bot")]))
+    [(Bot:) (fp "Bot")]
+    [(ImpFilter: a c) (fp "(ImpFilter ~a ~a)" a c)]))
 
 (define (print-pathelem c port write?)
   (define (fp . args) (apply fprintf port args))
diff --git a/collects/typed-scheme/utils/utils.ss b/collects/typed-scheme/utils/utils.ss
index 3fb7d363..ab40d625 100644
--- a/collects/typed-scheme/utils/utils.ss
+++ b/collects/typed-scheme/utils/utils.ss
@@ -145,7 +145,7 @@ at least theoretically.
 ;; - 1 printers have to be defined at the same time as the structs
 ;; - 2 we want to support things printing corectly even when the custom printer is off
 
-(define-for-syntax printing? #f)
+(define-for-syntax printing? #t)
 
 (define-syntax-rule (defprinter t ...)
   (begin