diff --git a/mozilla/layout/generic/nsHTMLReflowState.cpp b/mozilla/layout/generic/nsHTMLReflowState.cpp
index 0b715aa4baf..1959a3db516 100644
--- a/mozilla/layout/generic/nsHTMLReflowState.cpp
+++ b/mozilla/layout/generic/nsHTMLReflowState.cpp
@@ -1972,6 +1972,7 @@ nsHTMLReflowState::ComputeBlockBoxData(nsIPresContext* aPresContext,
         }
 
         AdjustComputedWidth(PR_FALSE);
+        CalculateBlockSideMargins(cbrs->mComputedWidth, mComputedWidth);
       }
     }
   } else {
diff --git a/mozilla/layout/html/base/src/nsHTMLReflowState.cpp b/mozilla/layout/html/base/src/nsHTMLReflowState.cpp
index 0b715aa4baf..1959a3db516 100644
--- a/mozilla/layout/html/base/src/nsHTMLReflowState.cpp
+++ b/mozilla/layout/html/base/src/nsHTMLReflowState.cpp
@@ -1972,6 +1972,7 @@ nsHTMLReflowState::ComputeBlockBoxData(nsIPresContext* aPresContext,
         }
 
         AdjustComputedWidth(PR_FALSE);
+        CalculateBlockSideMargins(cbrs->mComputedWidth, mComputedWidth);
       }
     }
   } else {