diff --git a/compiler-rt/lib/scudo/standalone/combined.h b/compiler-rt/lib/scudo/standalone/combined.h
--- a/compiler-rt/lib/scudo/standalone/combined.h
+++ b/compiler-rt/lib/scudo/standalone/combined.h
@@ -1155,7 +1155,8 @@
   // address tag in the first byte of the chunk.
   void storeEndMarker(uptr End, uptr Size, uptr BlockEnd) {
     uptr UntaggedEnd = untagPointer(End);
-    if (UntaggedEnd != BlockEnd) {
+    uptr UntaggedBlockEnd = untagPointer(BlockEnd);
+    if (UntaggedEnd != UntaggedBlockEnd) {
       storeTag(UntaggedEnd);
       if (Size == 0)
         *reinterpret_cast<u8 *>(UntaggedEnd) = extractTag(End);