diff --git a/racket/collects/racket/contract/private/blame.rkt b/racket/collects/racket/contract/private/blame.rkt
index 4f4c07151e..ccfcfe28ab 100644
--- a/racket/collects/racket/contract/private/blame.rkt
+++ b/racket/collects/racket/contract/private/blame.rkt
@@ -309,7 +309,7 @@
           (format "  contract from: ~a" from-negative-message))))
   
   (define custom-message-appears-to-start-with-fields?
-    (regexp-match? #rx"[^\n]*:" custom-message))
+    (regexp-match? #rx"^[^\n]*:" custom-message))
   
   (combine-lines
    (if custom-message-appears-to-start-with-fields?