diff --git a/layout/generic/FrameChildList.h b/layout/generic/FrameChildList.h
index 5e38a492dad..7bf6ba29c9c 100644
--- a/layout/generic/FrameChildList.h
+++ b/layout/generic/FrameChildList.h
@@ -96,9 +96,6 @@ protected:
   nsAutoTArray<FrameChildList,4> mLists;
 };
 
-} // namespace layout
-} // namespace mozilla
-
 inline mozilla::layout::FrameChildListIDs
 operator|(mozilla::layout::FrameChildListID aLeftOp,
           mozilla::layout::FrameChildListID aRightOp)
@@ -114,6 +111,9 @@ operator|(mozilla::layout::FrameChildListID aLeftOp,
   return mozilla::layout::FrameChildListIDs(aLeftOp) | aRightOp;
 }
 
+} // namespace layout
+} // namespace mozilla
+
 inline void nsFrameList::AppendIfNonempty(
          nsTArray<mozilla::layout::FrameChildList>* aLists,
          mozilla::layout::FrameChildListID aListID) const