diff --git a/Lex/Preprocessor.cpp b/Lex/Preprocessor.cpp
index 141536a..85a2c47 100644
--- a/Lex/Preprocessor.cpp
+++ b/Lex/Preprocessor.cpp
@@ -434,7 +434,7 @@
     DefineBuiltinMacro(Buf, "__int8=char");
     DefineBuiltinMacro(Buf, "__int16=short");
     DefineBuiltinMacro(Buf, "__int32=int");
-    DefineBuiltinMacro(Buf, "__int64=long");
+    DefineBuiltinMacro(Buf, "__int64=long long");
   }
   // FIXME: Should emit a #line directive here.
 }