diff --git a/dom/base/AbstractRange.cpp b/dom/base/AbstractRange.cpp
index e5454b4b1a1e..e362ad1fb73e 100644
--- a/dom/base/AbstractRange.cpp
+++ b/dom/base/AbstractRange.cpp
@@ -107,7 +107,10 @@ nsresult AbstractRange::SetStartAndEndInternal(
     // XXX: Offsets - handle this more efficiently.
     // If the end offset is less than the start offset, this should be
     // collapsed at the end offset.
-    if (aStartBoundary.Offset() > aEndBoundary.Offset()) {
+    if (*aStartBoundary.Offset(
+            RangeBoundaryBase<SPT, SRT>::OffsetFilter::kValidOffsets) >
+        *aEndBoundary.Offset(
+            RangeBoundaryBase<EPT, ERT>::OffsetFilter::kValidOffsets)) {
       aRange->DoSetRange(aEndBoundary, aEndBoundary, newStartRoot);
     } else {
       aRange->DoSetRange(aStartBoundary, aEndBoundary, newStartRoot);
diff --git a/dom/base/AbstractRange.h b/dom/base/AbstractRange.h
index 2eec3350b8a7..6d0c4efe6d85 100644
--- a/dom/base/AbstractRange.h
+++ b/dom/base/AbstractRange.h
@@ -50,17 +50,21 @@ class AbstractRange : public nsISupports, public nsWrapperCache {
 
   nsINode* GetStartContainer() const { return mStart.Container(); }
   nsINode* GetEndContainer() const { return mEnd.Container(); }
+
+  // FYI: Returns 0 if it's not positioned.
   uint32_t StartOffset() const {
-    // FYI: Returns 0 if it's not positioned.
-    return static_cast<uint32_t>(mStart.Offset());
+    return static_cast<uint32_t>(
+        *mStart.Offset(RangeBoundary::OffsetFilter::kValidOrInvalidOffsets));
   }
+
+  // FYI: Returns 0 if it's not positioned.
   uint32_t EndOffset() const {
-    // FYI: Returns 0 if it's not positioned.
-    return static_cast<uint32_t>(mEnd.Offset());
+    return static_cast<uint32_t>(
+        *mEnd.Offset(RangeBoundary::OffsetFilter::kValidOrInvalidOffsets));
   }
   bool Collapsed() const {
     return !mIsPositioned || (mStart.Container() == mEnd.Container() &&
-                              mStart.Offset() == mEnd.Offset());
+                              StartOffset() == EndOffset());
   }
 
   nsINode* GetParentObject() const { return mOwner; }
diff --git a/dom/base/RangeBoundary.h b/dom/base/RangeBoundary.h
index b39e9e50c833..35a8e5125916 100644
--- a/dom/base/RangeBoundary.h
+++ b/dom/base/RangeBoundary.h
@@ -100,10 +100,12 @@ class RangeBoundaryBase {
       return nullptr;
     }
     if (!mRef) {
-      MOZ_ASSERT(Offset() == 0, "invalid RangeBoundary");
+      MOZ_ASSERT(*Offset(OffsetFilter::kValidOrInvalidOffsets) == 0,
+                 "invalid RangeBoundary");
       return mParent->GetFirstChild();
     }
-    MOZ_ASSERT(mParent->GetChildAt_Deprecated(Offset()) ==
+    MOZ_ASSERT(mParent->GetChildAt_Deprecated(
+                   *Offset(OffsetFilter::kValidOrInvalidOffsets)) ==
                mRef->GetNextSibling());
     return mRef->GetNextSibling();
   }
@@ -204,7 +206,8 @@ class RangeBoundaryBase {
     if (Ref()) {
       return Ref()->GetParentNode() == Container();
     }
-    return Offset() <= Container()->Length();
+    return *Offset(OffsetFilter::kValidOrInvalidOffsets) <=
+           Container()->Length();
   }
 
   bool IsStartOfContainer() const {