diff --git a/include/clang/AST/Stmt.h b/include/clang/AST/Stmt.h
index 5a082b7..f119637 100644
--- a/include/clang/AST/Stmt.h
+++ b/include/clang/AST/Stmt.h
@@ -1636,7 +1636,7 @@
 public:
   MSAsmStmt(ASTContext &C, SourceLocation asmloc, bool issimple,
             bool isvolatile, ArrayRef<Token> asmtoks,
-            ArrayRef<unsigned> lineends, std::string &asmstr,
+            ArrayRef<unsigned> lineends, StringRef asmstr,
             SourceLocation endloc);
 
   SourceLocation getAsmLoc() const { return AsmLoc; }
diff --git a/lib/AST/Stmt.cpp b/lib/AST/Stmt.cpp
index e5ff75e..f676711 100644
--- a/lib/AST/Stmt.cpp
+++ b/lib/AST/Stmt.cpp
@@ -585,10 +585,10 @@
 
 MSAsmStmt::MSAsmStmt(ASTContext &C, SourceLocation asmloc,
                      bool issimple, bool isvolatile, ArrayRef<Token> asmtoks,
-                     ArrayRef<unsigned> lineends, std::string &asmstr,
+                     ArrayRef<unsigned> lineends, StringRef asmstr,
                      SourceLocation endloc)
   : Stmt(MSAsmStmtClass), AsmLoc(asmloc), EndLoc(endloc),
-    AsmStr(asmstr), IsSimple(issimple), IsVolatile(isvolatile),
+    AsmStr(asmstr.str()), IsSimple(issimple), IsVolatile(isvolatile),
     NumAsmToks(asmtoks.size()), NumLineEnds(lineends.size()) {
 
   AsmToks = new (C) Token[NumAsmToks];
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index 856a602..944fc40 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -2890,7 +2890,7 @@
 
   // Empty asm statements don't need to instantiate the AsmParser, etc.
   if (AsmToks.empty()) {
-    std::string AsmString;
+    StringRef AsmString;
     MSAsmStmt *NS =
       new (Context) MSAsmStmt(Context, AsmLoc, /* IsSimple */ true,
                               /* IsVolatile */ true, AsmToks, LineEnds,