diff --git a/racket/src/cs/rumble/error.ss b/racket/src/cs/rumble/error.ss
index 48e6e2abe5..8986626e19 100644
--- a/racket/src/cs/rumble/error.ss
+++ b/racket/src/cs/rumble/error.ss
@@ -664,10 +664,13 @@
        [else
         (|#%app|
          (cond
-          [(and (format-condition? v)
-                (or (string-prefix? "incorrect number of arguments" (condition-message v))
-                    (string-suffix? "values to single value return context" (condition-message v))
-                    (string-prefix? "incorrect number of values received in multiple value context" (condition-message v))))
+          [(or (and (format-condition? v)
+                    (or (string-prefix? "incorrect number of arguments" (condition-message v))
+                        (string-suffix? "values to single value return context" (condition-message v))
+                        (string-prefix? "incorrect number of values received in multiple value context" (condition-message v))))
+               (and (message-condition? v)
+                    (or (string-prefix? "incorrect argument count in call" (condition-message v))
+                        (string-prefix? "incorrect number of values from rhs" (condition-message v)))))
            exn:fail:contract:arity]
           [(and (format-condition? v)
                 (who-condition? v)
@@ -675,7 +678,8 @@
                 (string=? "undefined for ~s" (condition-message v)))
            exn:fail:contract:divide-by-zero]
           [(and (format-condition? v)
-                (string=? "attempt to reference undefined variable ~s" (condition-message v)))
+                (or (string=? "attempt to reference undefined variable ~s" (condition-message v))
+                    (string=? "attempt to assign undefined variable ~s" (condition-message v))))
            (lambda (msg marks)
              (|#%app| exn:fail:contract:variable msg marks (car (condition-irritants v))))]
           [else