diff --git a/js/src/gc/Marking.cpp b/js/src/gc/Marking.cpp
index 13ec5b0c05..1376df5a4d 100644
--- a/js/src/gc/Marking.cpp
+++ b/js/src/gc/Marking.cpp
@@ -788,7 +788,8 @@ ShouldMark<JSObject*>(GCMarker* gcmarker, JSObject* obj)
     // Don't mark things outside a zone if we are in a per-zone GC. It is
     // faster to check our own arena, which we can do since we know that
     // the object is tenured.
-    return obj->asTenured().zone()->shouldMarkInZone();
+    Zone* zone = obj->asTenured().zone();
+    return (zone && zone->shouldMarkInZone());
 }
 
 template <typename T>
diff --git a/js/src/vm/Runtime.cpp b/js/src/vm/Runtime.cpp
index ceb7a498b0..053b7c44b0 100644
--- a/js/src/vm/Runtime.cpp
+++ b/js/src/vm/Runtime.cpp
@@ -877,6 +877,9 @@ js::CurrentThreadCanAccessRuntime(const JSRuntime* rt)
 bool
 js::CurrentThreadCanAccessZone(Zone* zone)
 {
+    if (!zone)
+        return false;
+
     if (CurrentThreadCanAccessRuntime(zone->runtime_))
         return true;