--- a/dom/base/Selection.cpp
+++ b/dom/base/Selection.cpp
@@ -3210,19 +3210,19 @@ Selection::ContainsNode(nsINode& aNode, 
 {
   nsresult rv;
   if (mRanges.Length() == 0) {
     return false;
   }
 
   // XXXbz this duplicates the GetNodeLength code in nsRange.cpp
   uint32_t nodeLength;
-  bool isData = aNode.IsCharacterData();
-  if (isData) {
-    nodeLength = aNode.AsText()->TextLength();
+  auto* nodeAsCharData = CharacterData::FromNode(aNode);
+  if (nodeAsCharData) {
+    nodeLength = nodeAsCharData->TextLength();
   } else {
     nodeLength = aNode.GetChildCount();
   }
 
   nsTArray<nsRange*> overlappingRanges;
   rv = GetRangesForIntervalArray(&aNode, 0, &aNode, nodeLength,
                                  false, &overlappingRanges);
   if (NS_FAILED(rv)) {
@@ -3233,17 +3233,17 @@ Selection::ContainsNode(nsINode& aNode, 
     return false; // no ranges overlap
 
   // if the caller said partial intersections are OK, we're done
   if (aAllowPartial) {
     return true;
   }
 
   // text nodes always count as inside
-  if (isData) {
+  if (nodeAsCharData) {
     return true;
   }
 
   // The caller wants to know if the node is entirely within the given range,
   // so we have to check all intersecting ranges.
   for (uint32_t i = 0; i < overlappingRanges.Length(); i++) {
     bool nodeStartsBeforeRange, nodeEndsAfterRange;
     if (NS_SUCCEEDED(nsRange::CompareNodeToRange(&aNode, overlappingRanges[i],