diff --git a/lib/Demangle/ItaniumDemangle.cpp b/lib/Demangle/ItaniumDemangle.cpp
index b7e2e27ace5..8dd182fad15 100644
--- a/lib/Demangle/ItaniumDemangle.cpp
+++ b/lib/Demangle/ItaniumDemangle.cpp
@@ -17,7 +17,6 @@
 #include <cassert>
 #include <cctype>
 #include <cstdio>
-#include <cstddef>
 #include <cstdlib>
 #include <cstring>
 #include <numeric>
@@ -1951,7 +1950,7 @@ class BumpPointerAllocator {
   static constexpr size_t AllocSize = 4096;
   static constexpr size_t UsableAllocSize = AllocSize - sizeof(BlockMeta);
 
-  alignas(max_align_t) char InitialBuffer[AllocSize];
+  alignas(16) char InitialBuffer[AllocSize];
   BlockMeta* BlockList = nullptr;
 
   void grow() {