diff --git a/libguile/strings.c b/libguile/strings.c
index 2e766c28c..7bb277daf 100644
--- a/libguile/strings.c
+++ b/libguile/strings.c
@@ -1015,10 +1015,11 @@ SCM_DEFINE (scm_string, "string", 0, 0, 1,
 
   /* Verify that this is a list of chars.  */
   i = scm_ilength (chrs);
+  SCM_ASSERT (i >= 0, chrs, SCM_ARG1, FUNC_NAME);
+
   len = (size_t) i;
   rest = chrs;
 
-  SCM_ASSERT (len >= 0, chrs, SCM_ARG1, FUNC_NAME);
   while (len > 0 && scm_is_pair (rest))
     {
       SCM elt = SCM_CAR (rest);
diff --git a/test-suite/tests/strings.test b/test-suite/tests/strings.test
index d82a4723d..a35dd20d8 100644
--- a/test-suite/tests/strings.test
+++ b/test-suite/tests/strings.test
@@ -447,7 +447,17 @@
       (string-set! s 4 (integer->char #x010300))
       (char=? (string-ref s 4) (integer->char #x010300)))))
 
+;;
+;; list->string
+;;
+(with-test-prefix "string"
 
+  (pass-if-exception "convert circular list to string"
+     exception:wrong-type-arg
+     (let ((foo (list #\a #\b #\c)))
+       (set-cdr! (cddr foo) (cdr foo))
+       (apply string foo))))
+ 
 (with-test-prefix "string-split"
 
   ;; in guile 1.6.7 and earlier, character >=128 wasn't matched in the string