diff --git a/syndicate/syntax.rkt b/syndicate/syntax.rkt
index 257ce91..d328064 100644
--- a/syndicate/syntax.rkt
+++ b/syndicate/syntax.rkt
@@ -34,6 +34,7 @@
          this-target
          at
          assert
+         once
          stop-on
          on
          during
@@ -320,6 +321,9 @@
                                                      (->preserve expr)
                                                      (void)))))))])))
 
+(define-syntax-rule (once [event expr ...] ...)
+  (react (stop-on event expr ...) ...))
+
 (define-syntax-rule (stop-on event expr ...)
   (on event (stop-current-facet expr ...)))