diff --git a/pkgs/contract-profile/main.rkt b/pkgs/contract-profile/main.rkt
index daf7f861d7..50fdc221c7 100644
--- a/pkgs/contract-profile/main.rkt
+++ b/pkgs/contract-profile/main.rkt
@@ -15,7 +15,14 @@
   (define samples    (get-times (map cdr (reverse (cdr samples*)))))
   (define n-samples             (length contract-samples))
   ;; combine blame info and stack trace info. samples should line up
-  (define aug-contract-samples  (map cons contract-samples samples))
+  (define aug-contract-samples
+    (if (= (length contract-samples) (length samples))
+        (map cons contract-samples samples)
+        ;; This case happens on DrDr. Not sure how that's possible.
+        (begin (displayln contract-samples)
+               (displayln samples)
+               (error "contract-samples and samples are not of same length"
+                      (length contract-samples) " vs " (length samples)))))
   (define live-contract-samples (filter car aug-contract-samples))
   (define n-contract-samples    (length live-contract-samples))
   (define all-blames