diff --git a/appveyor.yml b/appveyor.yml
index 190d6fa9..c41150ee 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -21,7 +21,7 @@ environment:
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
       ARGS: --toolset=msvc-14.1 address-model=32
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      ARGS: --toolset=msvc-14.1 address-model=64 cxxflags=-std:c++latest
+      ARGS: --toolset=msvc-14.1 address-model=64 cxxflags=-std:c++latest cxxflags=-permissive-
     - ARGS: --toolset=msvc-9.0  address-model=32
     - ARGS: --toolset=msvc-10.0 address-model=32
     - ARGS: --toolset=msvc-11.0 address-model=32
diff --git a/include/boost/config/compiler/visualc.hpp b/include/boost/config/compiler/visualc.hpp
index f6b7ffae..8cbc20fb 100644
--- a/include/boost/config/compiler/visualc.hpp
+++ b/include/boost/config/compiler/visualc.hpp
@@ -338,7 +338,7 @@
 
 //
 // last known and checked version is 19.11.25506 (VC++ 2017.3):
-#if (_MSC_VER > 1911)
+#if (_MSC_VER > 1912)
 #  if defined(BOOST_ASSERT_CONFIG)
 #     error "Boost.Config is older than your current compiler version."
 #  elif !defined(BOOST_CONFIG_SUPPRESS_OUTDATED_MESSAGE)