--- a/layout/tables/nsTableFrame.cpp
+++ b/layout/tables/nsTableFrame.cpp
@@ -6449,38 +6449,41 @@ nsTableFrame::CalcBCBorders()
         //will know whether *this* row is at the bEnd
         const nsIFrame* nextRowGroup =
           ajaInfo.mRgAtStart ? ajaInfo.mRowGroup : nullptr;
         info.SetInnerRowGroupBEndContBCBorder(nextRowGroup, ajaInfo.mStartRow);
         gotRowBorder = true;
       }
     }
 
-    // see if the cell to the iEnd side had a rowspan and its bEnd-iStart border
-    // needs be joined with this one's bEnd
-    // if  there is a cell to the iEnd and the cell to iEnd side was a rowspan
-    if ((info.mNumTableCols != info.GetCellEndColIndex() + 1) &&
-        (lastBEndBorders[info.GetCellEndColIndex() + 1].rowSpan > 1) &&
-        (lastBEndBorders[info.GetCellEndColIndex() + 1].rowIndex ==
-         info.GetCellEndRowIndex() + 1)) {
-      BCCornerInfo& corner = bEndCorners[info.GetCellEndColIndex() + 1];
-      if (!IsBlock(LogicalSide(corner.ownerSide))) {
-        // not a block-dir owner
-        BCCellBorder& thisBorder = lastBEndBorder;
-        BCCellBorder& nextBorder = lastBEndBorders[info.mColIndex + 1];
-        if ((thisBorder.color == nextBorder.color) &&
-            (thisBorder.width == nextBorder.width) &&
-            (thisBorder.style == nextBorder.style)) {
-          // set the flag on the next border indicating it is not the start of a
-          // new segment
-          if (iter.mCellMap) {
-            tableCellMap->ResetBStartStart(eLogicalSideBEnd, *iter.mCellMap,
-                                           iter.mRowGroupStart,
-                                           info.GetCellEndRowIndex(),
-                                           info.GetCellEndColIndex() + 1);
+    // When the cell to the IEnd side has row span, the cell's BEnd border
+    // need to be checked if it can be joined to this cell's BEnd.
+    // We have to do this check here because the code above will only
+    // check the cell's IStart side's cell's BEnd. So in the case of a cell with
+    // row span, the cell's final BEnd's border's IEnd side border has not been
+    // updated yet. That's why we have to do this here.
+    if ((info.mNumTableCols != info.GetCellEndColIndex() + 1)) {
+      // We query |info.GetCellEndColIndex() + 1| which let us get the BEnd border
+      // from previous row's BEnd. And if we have a row span to the IEnd side, we
+      // can get the cell to the IEnd side's BEnd border.
+      BCCellBorder& previousBorder = lastBEndBorders[info.GetCellEndColIndex() + 1];
+      // add 1 to the info.GetCellEndRowIndex()
+      if (previousBorder.rowSpan > 1 &&
+          previousBorder.rowIndex == info.GetCellEndRowIndex() + 1) {
+        BCCornerInfo& corner = bEndCorners[info.GetCellEndColIndex() + 1];
+        if (!IsBlock(LogicalSide(corner.ownerSide))) {
+          if ((lastBEndBorder.color == previousBorder.color) &&
+              (lastBEndBorder.width == previousBorder.width) &&
+              (lastBEndBorder.style == previousBorder.style)) {
+            if (iter.mCellMap) {
+              tableCellMap->ResetBStartStart(eLogicalSideBEnd, *iter.mCellMap,
+                                             iter.mRowGroupStart,
+                                             info.GetCellEndRowIndex(),
+                                             info.GetCellEndColIndex() + 1);
+            }
           }
         }
       }
     }
   } // for (iter.First(info); info.mCell; iter.Next(info)) {
   // reset the bc flag and damage area
   SetNeedToCalcBCBorders(false);
   propData->mDamageArea = TableArea(0, 0, 0, 0);