--- a/layout/xul/nsSprocketLayout.cpp
+++ b/layout/xul/nsSprocketLayout.cpp
@@ -760,17 +760,16 @@ nsSprocketLayout::PopulateBoxSizes(nsIFr
       AddMargin(child, maxSize);
     }
 
     if (!currentBox) {
       // create one.
       currentBox = new (aState) nsBoxSize();
       if (!aBoxSizes) {
         aBoxSizes = currentBox;
-        last = aBoxSizes;
       } else {
         last->next = currentBox;
         last = currentBox;
       }
 
       nscoord minWidth;
       nscoord maxWidth;
       nscoord prefWidth;