diff --git a/compiler-rt/lib/msan/msan_poisoning.cpp b/compiler-rt/lib/msan/msan_poisoning.cpp
--- a/compiler-rt/lib/msan/msan_poisoning.cpp
+++ b/compiler-rt/lib/msan/msan_poisoning.cpp
@@ -56,8 +56,6 @@
   }
 
   uptr end = (d + size) & ~3UL;
-  // If both ends fall into the same 4-byte slot, we are done.
-  if (end < beg) return;
 
   // Copy right unaligned origin if that memory is poisoned.
   if (end < d + size) {