diff --git a/docshell/base/timeline/JavascriptTimelineMarker.h b/docshell/base/timeline/JavascriptTimelineMarker.h
index 47c9943a5e7f..5a99242831b8 100644
--- a/docshell/base/timeline/JavascriptTimelineMarker.h
+++ b/docshell/base/timeline/JavascriptTimelineMarker.h
@@ -62,7 +62,8 @@ public:
           return;
         }
 
-        if (!JS::CopyAsyncStack(aCx, asyncStack, asyncCause, &parentFrame, 0)) {
+        if (JS::IsSavedFrame(asyncStack) &&
+            !JS::CopyAsyncStack(aCx, asyncStack, asyncCause, &parentFrame, 0)) {
           JS_ClearPendingException(aCx);
         } else {
           stackFrame.mAsyncParent = parentFrame;
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index e4cdc12737d9..7610d556ca92 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -5996,6 +5996,13 @@ GetSavedFrameParent(JSContext* cx, HandleObject savedFrame, MutableHandleObject
 extern JS_PUBLIC_API(bool)
 BuildStackString(JSContext* cx, HandleObject stack, MutableHandleString stringp, size_t indent = 0);
 
+/**
+ * Return true iff the given object is either a SavedFrame object or wrapper
+ * around a SavedFrame object, and it is not the SavedFrame.prototype object.
+ */
+extern JS_PUBLIC_API(bool)
+IsSavedFrame(JSObject* obj);
+
 } /* namespace JS */
 
 
diff --git a/js/src/vm/SavedStacks.cpp b/js/src/vm/SavedStacks.cpp
index a224bfe57973..5c0588d9d56b 100644
--- a/js/src/vm/SavedStacks.cpp
+++ b/js/src/vm/SavedStacks.cpp
@@ -930,6 +930,19 @@ BuildStackString(JSContext* cx, HandleObject stack, MutableHandleString stringp,
     return true;
 }
 
+JS_PUBLIC_API(bool)
+IsSavedFrame(JSObject* obj)
+{
+    if (!obj)
+        return false;
+
+    JSObject* unwrapped = CheckedUnwrap(obj);
+    if (!unwrapped)
+        return false;
+
+    return js::SavedFrame::isSavedFrameAndNotProto(*unwrapped);
+}
+
 } /* namespace JS */
 
 namespace js {