diff --git a/src/main/cljs/cljs/spec.cljs b/src/main/cljs/cljs/spec.cljs
index ada8ec69fb..331d79aedc 100644
--- a/src/main/cljs/cljs/spec.cljs
+++ b/src/main/cljs/cljs/spec.cljs
@@ -425,7 +425,7 @@
        (gen* [_ _ _ _] (if gfn
                          (gfn)
                          (gen/gen-for-pred pred)))
-       (with-gen* [_ gfn] (spec-impl form pred gfn cpred?))
+       (with-gen* [_ gfn] (spec-impl form pred gfn cpred? unc))
        (describe* [_] form)))))
 
 (defn ^:skip-wiki multi-spec-impl