diff --git a/layout/generic/nsContainerFrame.cpp b/layout/generic/nsContainerFrame.cpp
index 23347a084c4..c5370107d4b 100644
--- a/layout/generic/nsContainerFrame.cpp
+++ b/layout/generic/nsContainerFrame.cpp
@@ -660,8 +660,10 @@ nsContainerFrame::DoInlineIntrinsicWidth(nsIRenderingContext *aRenderingContext,
     styleBorder->GetBorderWidth(startSide) +
     GetCoord(styleMargin->mMargin.Get(startSide, tmp), 0);
 
-  for (nsContainerFrame *nif = this; nif;
-       nif = (nsContainerFrame*) nif->GetNextInFlow()) {
+  const nsLineList_iterator* savedLine = aData->line;
+  nsContainerFrame* next;
+
+  for (nsContainerFrame *nif = this; nif; nif = next) {
     for (nsIFrame *kid = nif->mFrames.FirstChild(); kid;
          kid = kid->GetNextSibling()) {
       if (aType == nsLayoutUtils::MIN_WIDTH)
@@ -671,7 +673,16 @@ nsContainerFrame::DoInlineIntrinsicWidth(nsIRenderingContext *aRenderingContext,
         kid->AddInlinePrefWidth(aRenderingContext,
                                 static_cast<InlinePrefWidthData*>(aData));
     }
+    
+    next = (nsContainerFrame*) nif->GetNextInFlow();
+    if (next) {
+      // After we advance to our next-in-flow, the stored line may no
+      // longer be the correct line. Just forget it.
+      aData->line = nsnull;
+    }
   }
+  
+  aData->line = savedLine;
 
   // This goes at the end no matter how things are broken and how
   // messy the bidi situations are, since per CSS2.1 section 8.6
diff --git a/layout/generic/nsIFrame.h b/layout/generic/nsIFrame.h
index f57e8aed825..3e4ab416a65 100644
--- a/layout/generic/nsIFrame.h
+++ b/layout/generic/nsIFrame.h
@@ -1146,7 +1146,8 @@ public:
       , trailingWhitespace(0)
     {}
 
-    // The line. This may be null if the inlines are not associated with a block.
+    // The line. This may be null if the inlines are not associated with
+    // a block or if we just don't know the line.
     const nsLineList_iterator* line;
 
     // The maximum intrinsic width for all previous lines.