diff --git a/collects/deinprogramm/signature/signature-unit.rkt b/collects/deinprogramm/signature/signature-unit.rkt
index 1e20bf2096..2059bb7fc4 100644
--- a/collects/deinprogramm/signature/signature-unit.rkt
+++ b/collects/deinprogramm/signature/signature-unit.rkt
@@ -195,8 +195,8 @@
 	   (if (andmap eq? orig els)
 	       obj
 	       (let ((new (list->vector els)))
-		 (hash-set! vectors-table obj new old-sigs)
-		 obj)))))
+		 (hash-set! vectors-table obj old-sigs)
+		 new)))))
 
      (cond
       ((not (vector? obj))
diff --git a/collects/tests/deinprogramm/signature.rkt b/collects/tests/deinprogramm/signature.rkt
index 54e47a2762..1a52196007 100644
--- a/collects/tests/deinprogramm/signature.rkt
+++ b/collects/tests/deinprogramm/signature.rkt
@@ -88,9 +88,12 @@
  
    (test-case
     "vector"
-    (define integer-vector (make-vector-signature 'integer-list integer #f))
+    (define integer-vector (make-vector-signature 'integer-vector integer #f))
+    (define a-vector (make-vector-signature 'a-vector %a #f))
     (check-equal? (say-no (apply-signature integer-vector '#(1 2 3)))
 		  '#(1 2 3))
+    (check-equal? (say-no (apply-signature a-vector '#(1 2 3)))
+		  '#(1 2 3))
     (check-equal? (say-no (apply-signature integer-vector '#f))
 		  'no)
     (check-eq? (failed-signature (apply-signature integer-vector '#(1 #f 3)))