diff --git a/js/src/builtin/ModuleObject.cpp b/js/src/builtin/ModuleObject.cpp
index 44e5a2c887..728929e8c0 100644
--- a/js/src/builtin/ModuleObject.cpp
+++ b/js/src/builtin/ModuleObject.cpp
@@ -272,7 +272,7 @@ IndirectBindingMap::put(JSContext* cx, HandleId name,
     // different zone to the final module. Lazily allocate the map so we don't
     // have to switch its zone when merging compartments.
     if (!map_) {
-        MOZ_ASSERT(!cx->zone()->group()->createdForHelperThread());
+        MOZ_ASSERT(!cx->zone()->usedByExclusiveThread);
         map_.emplace(cx->zone());
         if (!map_->init()) {
             map_.reset();