diff --git a/collects/tests/racket/contract-test.rktl b/collects/tests/racket/contract-test.rktl
index dd93b870c4..0286c604f5 100644
--- a/collects/tests/racket/contract-test.rktl
+++ b/collects/tests/racket/contract-test.rktl
@@ -4350,6 +4350,25 @@
       (with-continuation-mark mark (lambda (x) (+ x 1))
         (do-mark mark))))
 
+  (test/pos-blame
+   'continuation-mark-key/c-ho-10
+   '(let* ([mark (make-continuation-mark-key)]
+           [ctc-mark (contract (continuation-mark-key/c number?)
+                               mark
+                               'pos
+                               'neg)])
+      (with-continuation-mark mark "not a number"
+        (+ 1 (continuation-mark-set-first #f ctc-mark)))))
+
+  (test/spec-passed
+   'continuation-mark-key/c-ho-11
+   '(let* ([mark (make-continuation-mark-key)]
+           [ctc-mark (contract (continuation-mark-key/c number?)
+                               mark
+                               'pos
+                               'neg)])
+      (continuation-mark-set-first #f ctc-mark)))
+
   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   ;;
   ;;  make-contract
diff --git a/src/racket/src/fun.c b/src/racket/src/fun.c
index a251f97e59..1bdad50a0b 100644
--- a/src/racket/src/fun.c
+++ b/src/racket/src/fun.c
@@ -7889,6 +7889,9 @@ scheme_extract_one_cc_mark_with_meta(Scheme_Object *mark_set, Scheme_Object *key
 	}
       }
 
+      if (key_arg != key && val != NULL)
+        val = scheme_chaperone_do_continuation_mark("continuation-mark-set-first", 1, key_arg, val);
+
       pos = startpos - findpos;
       if (pos > 16) {
         pos >>= 1;
@@ -7931,8 +7934,6 @@ scheme_extract_one_cc_mark_with_meta(Scheme_Object *mark_set, Scheme_Object *key
           } else
             cht = NULL;
 
-          if (key_arg != key)
-            val = scheme_chaperone_do_continuation_mark("continuation-mark-set-first", 1, key_arg, val);
           if (!cache || !SCHEME_VECTORP(cache)) {
             /* No cache so far, so map one key */
             cache = scheme_make_vector(4, NULL);