diff --git a/pkgs/racket-test-core/tests/racket/sync.rktl b/pkgs/racket-test-core/tests/racket/sync.rktl
index 7b8d205de8..77e5b962a5 100644
--- a/pkgs/racket-test-core/tests/racket/sync.rktl
+++ b/pkgs/racket-test-core/tests/racket/sync.rktl
@@ -1651,6 +1651,26 @@
     (sync s))
   (thread-wait t))
 
+;; ----------------------------------------
+;; regression test to check that when a choice evt replaces a single
+;; event, an already-chosen event (perhaps represented as an index) is
+;; not misinterpreted later
+
+(for ([i (in-range 10)])
+  (define ch (make-channel))
+  (define v
+    (sync (guard-evt
+           (lambda ()
+             (thread (lambda () (channel-put ch 0)))
+             (sync (system-idle-evt))
+             (choice-evt
+              (wrap-evt always-evt (lambda (v) 1))
+              (wrap-evt always-evt (lambda (v) 2))
+              (wrap-evt always-evt (lambda (v) 3)))))
+          ch))
+  (unless (memq v '(0 1 2 3))
+    (error "bad sync result" v)))
+
 ;; ----------------------------------------
 
 (report-errs)
diff --git a/racket/src/bc/src/thread.c b/racket/src/bc/src/thread.c
index b18e6448f9..b18f98b569 100644
--- a/racket/src/bc/src/thread.c
+++ b/racket/src/bc/src/thread.c
@@ -6560,7 +6560,10 @@ static void set_sync_target(Syncing *syncing, int i, Scheme_Object *target,
       /* Inline the set (in place) */
       Scheme_Object **argv;
       Evt **ws;
-       
+
+      if (syncing->result > i+1)
+        syncing->result += wts->argc-1;
+
       argv = (Scheme_Object **)splice_ptr_array((void **)evt_set->argv, 
 						evt_set->argc,
 						(void **)wts->argv,