diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -1587,9 +1587,15 @@
 
   for (GlobalVariable *GV : Globals) {
     Tag &= TagMaskByte;
-    // Skip tag 0 in order to avoid collisions with untagged memory.
-    if (Tag == 0)
+    if (ClUseShortGranules && Tag < 16) {
+      // Don't allow globals to be tagged with something that looks like a
+      // short-granule tag, otherwise we lose inter-granule overflow detection,
+      // as the fast path shadow-vs-address check succeeds.
+      Tag = 16;
+    } else if (Tag == 0) {
+      // Skip tag 0 in order to avoid collisions with untagged memory.
       Tag = 1;
+    }
     instrumentGlobal(GV, Tag++);
   }
 }