diff --git a/layout/generic/nsBlockFrame.cpp b/layout/generic/nsBlockFrame.cpp
index 44e80cf4c681..7a9b22647b89 100644
--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -1001,7 +1001,7 @@ nsBlockFrame::Reflow(nsPresContext*           aPresContext,
   DrainOverflowLines(state);
 
   // Handle paginated overflow (see nsContainerFrame.h)
-  nsRect ocBounds;
+  nsOverflowAreas ocBounds;
   nsReflowStatus ocStatus = NS_FRAME_COMPLETE;
   if (GetPrevInFlow()) {
     ReflowOverflowContainerChildren(aPresContext, aReflowState, ocBounds, 0,
@@ -1103,7 +1103,7 @@ nsBlockFrame::Reflow(nsPresContext*           aPresContext,
   ComputeFinalSize(aReflowState, state, aMetrics, &bottomEdgeOfChildren);
   ComputeCombinedArea(aReflowState, aMetrics, bottomEdgeOfChildren);
   // Factor overflow container child bounds into the overflow area
-  aMetrics.mOverflowArea.UnionRect(aMetrics.mOverflowArea, ocBounds);
+  aMetrics.mOverflowAreas.UnionWith(ocBounds);
   // Factor pushed float child bounds into the overflow area
   aMetrics.mOverflowArea.UnionRect(aMetrics.mOverflowArea, fcBounds);
 
diff --git a/layout/generic/nsCanvasFrame.cpp b/layout/generic/nsCanvasFrame.cpp
index 8cc359e7ee22..dc0354186f43 100644
--- a/layout/generic/nsCanvasFrame.cpp
+++ b/layout/generic/nsCanvasFrame.cpp
@@ -597,7 +597,7 @@ nsCanvasFrame::Reflow(nsPresContext*           aPresContext,
 
   if (prevCanvasFrame) {
     ReflowOverflowContainerChildren(aPresContext, aReflowState,
-                                    aDesiredSize.mOverflowArea, 0,
+                                    aDesiredSize.mOverflowAreas, 0,
                                     aStatus);
   }
 
diff --git a/layout/generic/nsContainerFrame.cpp b/layout/generic/nsContainerFrame.cpp
index 0d92200d3ac5..817051c74289 100644
--- a/layout/generic/nsContainerFrame.cpp
+++ b/layout/generic/nsContainerFrame.cpp
@@ -856,7 +856,7 @@ nsContainerFrame::FinishReflowChild(nsIFrame*                  aKidFrame,
 nsresult
 nsContainerFrame::ReflowOverflowContainerChildren(nsPresContext*           aPresContext,
                                                   const nsHTMLReflowState& aReflowState,
-                                                  nsRect&                  aOverflowRect,
+                                                  nsOverflowAreas&         aOverflowRects,
                                                   PRUint32                 aFlags,
                                                   nsReflowStatus&          aStatus)
 {
@@ -993,7 +993,7 @@ nsContainerFrame::ReflowOverflowContainerChildren(nsPresContext*           aPres
       if (aReflowState.mFloatManager)
         nsBlockFrame::RecoverFloatsFor(frame, *aReflowState.mFloatManager);
     }
-    ConsiderChildOverflow(aOverflowRect, frame);
+    ConsiderChildOverflow(aOverflowRects, frame);
   }
 
   return NS_OK;
diff --git a/layout/generic/nsContainerFrame.h b/layout/generic/nsContainerFrame.h
index bbefc5506f64..f4c670f11ab1 100644
--- a/layout/generic/nsContainerFrame.h
+++ b/layout/generic/nsContainerFrame.h
@@ -277,7 +277,7 @@ public:
    */
   nsresult ReflowOverflowContainerChildren(nsPresContext*           aPresContext,
                                            const nsHTMLReflowState& aReflowState,
-                                           nsRect&                  aOverflowRect,
+                                           nsOverflowAreas&         aOverflowRects,
                                            PRUint32                 aFlags,
                                            nsReflowStatus&          aStatus);