diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index 1fd2ae4b409..72f3aa402e5 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -2941,11 +2941,14 @@ nsDocShell::PopProfileTimelineMarkers(JSContext* aCx,
     }
   }
 
-  ToJSValue(aCx, profileTimelineMarkers, aProfileTimelineMarkers);
-
   ClearProfileTimelineMarkers();
   mProfileTimelineMarkers.SwapElements(keptMarkers);
 
+  if (!ToJSValue(aCx, profileTimelineMarkers, aProfileTimelineMarkers)) {
+    JS_ClearPendingException(aCx);
+    return NS_ERROR_UNEXPECTED;
+  }
+
   return NS_OK;
 #else
   return NS_ERROR_FAILURE;