JS interop breaks after merge-opts

[borkdude]

cljs.user=> (def ctx (sci/init {:classes {'js goog/global :allow :all}}))
#'cljs.user/ctx
cljs.user=> (sci/eval-string* ctx "(try (assoc 1 1 1) (catch js/Error e 12))" )
12
cljs.user=> (def ctx2 (sci/merge-opts ctx {:namespaces {}}))
#'cljs.user/ctx2
cljs.user=> (sci/eval-string* ctx2 "(try (assoc 1 1 1) (catch js/Error e 12))" )
Execution error (ExceptionInfo) at (<cljs repl>:1).
Unable to resolve classname: js/Error