diff --git a/include/llvm/ADT/StringMap.h b/include/llvm/ADT/StringMap.h
index 0d68d11a12f..978ec443032 100644
--- a/include/llvm/ADT/StringMap.h
+++ b/include/llvm/ADT/StringMap.h
@@ -237,6 +237,9 @@ public:
   explicit StringMap(AllocatorTy A)
     : StringMapImpl(static_cast<unsigned>(sizeof(MapEntryTy))), Allocator(A) {}
 
+  StringMap(unsigned InitialSize, AllocatorTy A)
+    : StringMapImpl(InitialSize), Allocator(A) {}
+
   StringMap(const StringMap &RHS)
     : StringMapImpl(static_cast<unsigned>(sizeof(MapEntryTy))) {
     assert(RHS.empty() &&