diff --git a/collects/mzlib/private/match/convert-pat.ss b/collects/mzlib/private/match/convert-pat.ss
index a3c1dceac2..49c092dce4 100644
--- a/collects/mzlib/private/match/convert-pat.ss
+++ b/collects/mzlib/private/match/convert-pat.ss
@@ -1,7 +1,8 @@
 (module convert-pat mzscheme
   (require "match-error.ss"
            "match-helper.ss"
-           "match-expander-struct.ss")
+           "match-expander-struct.ss"
+           "observe-step.ss")
 
   (require-for-template mzscheme
 			"match-error.ss")
@@ -84,13 +85,15 @@
 		[xformer (match-expander-match-xform expander)])
 	   (if (not xformer)
 	       (match:syntax-err #'expander
-				 "This expander only works with plt-match.")
-	       (let ([introducer (make-syntax-introducer)]
-		     [certifier (match-expander-certifier expander)])
-		 (convert-pat/cert
-		  (introducer (xformer (introducer stx)))
-		  (lambda (id)
-		    (certifier (cert id) #f introducer))))))]
+				 "This expander only works with plt-match.ss.")
+	       (let* ([introducer (make-syntax-introducer)]
+                      [certifier (match-expander-certifier expander)]
+                      [mstx (introducer stx)]
+                      [mresult (xformer mstx)]
+                      [result (introducer mresult)]
+                      [cert* (lambda (id) (certifier (cert id) #f introducer))])
+                 (observe-step stx mstx mresult result)
+                 (convert-pat/cert result cert*))))]
 	[p
 	 (dot-dot-k? (syntax-object->datum #'p))
 	 stx]
diff --git a/collects/mzlib/private/match/observe-step.ss b/collects/mzlib/private/match/observe-step.ss
new file mode 100644
index 0000000000..bb2cba7f0e
--- /dev/null
+++ b/collects/mzlib/private/match/observe-step.ss
@@ -0,0 +1,43 @@
+(module observe-step mzscheme
+  (provide observe-step)
+  
+    (define current-expand-observe
+    (dynamic-require '#%expobs 'current-expand-observe))
+  
+  (define (observe-step pre mpre mpost post)
+    (define (call-obs ev . args) 
+      (let ([obs (current-expand-observe)])
+        (if obs 
+            (let ([evn (case ev
+                         [(visit) 0]
+                         [(enter-prim) 6]
+                         [(prim-stop) 100]
+                         [(exit-prim) 7]
+                         [(return) 2]
+                         [(macro-enter) 8]
+                         [(macro-exit) 9]
+                         [(macro-pre) 21]
+                         [(macro-post) 22]
+                         [(local-enter) 130]
+                         [(local-exit) 131]
+                         [(local-pre) 132]
+                         [(local-post) 133])])
+              (apply obs evn args)))))
+    
+    (call-obs 'local-enter pre)
+    (call-obs 'local-pre pre)
+    (call-obs 'visit pre)
+    (call-obs 'macro-enter pre)
+    (call-obs 'macro-pre mpre)
+    (call-obs 'macro-post mpost)
+    (call-obs 'macro-exit post)
+    (call-obs 'visit post)
+    (call-obs 'enter-prim post)
+    (call-obs 'prim-stop #f)
+    (call-obs 'exit-prim post)
+    (call-obs 'return post)
+    (call-obs 'local-post post)
+    (call-obs 'local-exit post)
+    )
+
+  )
\ No newline at end of file
diff --git a/collects/mzlib/private/match/simplify-patterns.ss b/collects/mzlib/private/match/simplify-patterns.ss
index 558e48f4aa..fac49fa7d7 100644
--- a/collects/mzlib/private/match/simplify-patterns.ss
+++ b/collects/mzlib/private/match/simplify-patterns.ss
@@ -11,7 +11,8 @@
            "update-binding-counts.scm"
            "reorder-tests.scm"
            "match-expander-struct.ss"
-           "render-helpers.ss")
+           "render-helpers.ss"
+           "observe-step.ss")
   
   (require "render-sigs.ss"
            (lib "unitsig.ss"))
@@ -26,44 +27,6 @@
                         "match-helper.ss")
   
 
-  (define current-expand-observe
-    (dynamic-require '#%expobs 'current-expand-observe))
-  
-  (define (observe-step pre mpre mpost post)
-    (define (call-obs ev . args) 
-      (let ([obs (current-expand-observe)])
-        (if obs 
-            (let ([evn (case ev
-                         [(visit) 0]
-                         [(enter-prim) 6]
-                         [(prim-stop) 100]
-                         [(exit-prim) 7]
-                         [(return) 2]
-                         [(macro-enter) 8]
-                         [(macro-exit) 9]
-                         [(macro-pre) 21]
-                         [(macro-post) 22]
-                         [(local-enter) 130]
-                         [(local-exit) 131]
-                         [(local-pre) 132]
-                         [(local-post) 133])])
-              (apply obs evn args)))))
-    
-    (call-obs 'local-enter pre)
-    (call-obs 'local-pre pre)
-    (call-obs 'visit pre)
-    (call-obs 'macro-enter pre)
-    (call-obs 'macro-pre mpre)
-    (call-obs 'macro-post mpost)
-    (call-obs 'macro-exit post)
-    (call-obs 'visit post)
-    (call-obs 'enter-prim post)
-    (call-obs 'prim-stop #f)
-    (call-obs 'exit-prim post)
-    (call-obs 'return post)
-    (call-obs 'local-post post)
-    (call-obs 'local-exit post)
-    )
 
   (provide simplify)