--- a/layout/generic/nsBlockFrame.cpp
+++ b/layout/generic/nsBlockFrame.cpp
@@ -3399,17 +3399,17 @@ nsBlockFrame::ReflowBlockFrame(nsBlockRe
       // reflow again.
       if (!replacedBlock) {
         break;
       }
 
       LogicalRect oldFloatAvailableSpaceRect(floatAvailableSpace.mRect);
       floatAvailableSpace = aState.GetFloatAvailableSpaceForBSize(
                               aState.mBCoord + bStartMargin,
-                              brc.GetMetrics().Height(),
+                              brc.GetMetrics().BSize(wm),
                               &floatManagerState);
       NS_ASSERTION(floatAvailableSpace.mRect.BStart(wm) ==
                      oldFloatAvailableSpaceRect.BStart(wm),
                    "yikes");
       // Restore the height to the position of the next band.
       floatAvailableSpace.mRect.BSize(wm) =
         oldFloatAvailableSpaceRect.BSize(wm);
       // Determine whether the available space shrunk on either side,