diff --git a/collects/tests/racket/optimize.rktl b/collects/tests/racket/optimize.rktl
index 8430cd12ec..b6bb9a37cd 100644
--- a/collects/tests/racket/optimize.rktl
+++ b/collects/tests/racket/optimize.rktl
@@ -872,6 +872,7 @@
 	  [t2 (get-output-bytes s2)])
       (or (bytes=? t1 t2)
 	  (begin
+            #;
 	    (printf "~s\n~s\n" 
                     (zo-parse (open-input-bytes t1))
                     (zo-parse (open-input-bytes t2)))
@@ -3015,6 +3016,33 @@
                #f "")
   )
 
+
+;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;; Make sure the compiler unboxes the `v'
+;; argument in the loop below:
+
+(let ()
+  (define l '(module m racket/base
+               (require racket/flonum)
+               (define (f)
+                 (let loop ([n 1000][v 0.0])
+                   (if (zero? n)
+                       v
+                       (loop (- n 1)
+                             (fl+ v 2.0)))))))
+  (define b
+    (let ([o (open-output-bytes)])
+      (write (compile l) o)
+      (parameterize ([read-accept-compiled #t])
+        (zo-parse (open-input-bytes (get-output-bytes o))))))
+  (let* ([m (compilation-top-code b)]
+         [d (car (mod-body m))]
+         [b (closure-code (def-values-rhs d))]
+         [c (application-rator (lam-body b))]
+         [l (closure-code c)]
+         [ts (lam-param-types l)])
+    (test 'flonum cadr ts)))
+
 ;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 
diff --git a/src/racket/src/optimize.c b/src/racket/src/optimize.c
index b797fd1180..79fa952a5a 100644
--- a/src/racket/src/optimize.c
+++ b/src/racket/src/optimize.c
@@ -4925,12 +4925,21 @@ static void merge_closure_local_type_map(Scheme_Closure_Data *data1, Scheme_Clos
       cl2->has_tymap = 1;
       cl2->local_type_map = cl1->local_type_map;
     } else if (cl2->local_type_map) {
-      int i;
+      int i, recheck = 0;
       for (i = data1->num_params; i--; ) {
         if (cl1->local_type_map[i] != cl2->local_type_map[i]) {
-          cl2->local_type_map = NULL;
+          cl1->local_type_map[i] = 0;
+          cl2->local_type_map[i] = 0;
+          recheck = 1;
+        }
+      }
+      if (recheck) {
+        for (i = data1->num_params; i--; ) {
+          if (cl1->local_type_map[i]) break;
+        }
+        if (i < 0) {
           cl1->local_type_map = NULL;
-          break;
+          cl2->local_type_map = NULL;
         }
       }
     } else {