diff --git a/combined.h b/combined.h
index e8bb8bf..fd5360c 100644
--- a/combined.h
+++ b/combined.h
@@ -639,7 +639,7 @@
           if (ClassId) {
             resizeTaggedChunk(reinterpret_cast<uptr>(OldTaggedPtr) + OldSize,
                               reinterpret_cast<uptr>(OldTaggedPtr) + NewSize,
-                              NewSize, BlockEnd);
+                              NewSize, untagPointer(BlockEnd));
             storePrimaryAllocationStackMaybe(Options, OldPtr);
           } else {
             storeSecondaryAllocationStackMaybe(Options, OldPtr, NewSize);
@@ -1154,6 +1154,7 @@
   // address tags against chunks. To allow matching in this case we store the
   // address tag in the first byte of the chunk.
   void storeEndMarker(uptr End, uptr Size, uptr BlockEnd) {
+    DCHECK_EQ(BlockEnd, untagPointer(BlockEnd));
     uptr UntaggedEnd = untagPointer(End);
     if (UntaggedEnd != BlockEnd) {
       storeTag(UntaggedEnd);