diff --git a/clang/lib/Basic/Targets/OSTargets.cpp b/clang/lib/Basic/Targets/OSTargets.cpp
--- a/clang/lib/Basic/Targets/OSTargets.cpp
+++ b/clang/lib/Basic/Targets/OSTargets.cpp
@@ -180,7 +180,7 @@
 
     if (Opts.isCompatibleWithMSVC(LangOptions::MSVC2015)) {
       if (Opts.CPlusPlus2a)
-        Builder.defineMacro("_MSVC_LANG", "201704L");
+        Builder.defineMacro("_MSVC_LANG", "201705L");
       else if (Opts.CPlusPlus17)
         Builder.defineMacro("_MSVC_LANG", "201703L");
       else if (Opts.CPlusPlus14)
diff --git a/clang/test/Preprocessor/predefined-win-macros.c b/clang/test/Preprocessor/predefined-win-macros.c
--- a/clang/test/Preprocessor/predefined-win-macros.c
+++ b/clang/test/Preprocessor/predefined-win-macros.c
@@ -47,7 +47,7 @@
 // RUN: %clang_cc1 %s -x c++ -E -dM -triple i686-pc-win32 -fms-extensions -fms-compatibility \
 // RUN:     -fms-compatibility-version=19.00 -std=c++2a -o - | FileCheck -match-full-lines %s --check-prefix=CHECK-MS-CPP2A
 // CHECK-MS-CPP2A: #define _MSC_VER 1900
-// CHECK-MS-CPP2A: #define _MSVC_LANG 201704L
+// CHECK-MS-CPP2A: #define _MSVC_LANG 201705L
 
 // RUN: %clang_cc1 -triple i386-windows %s -E -dM -o - \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-X86-WIN