diff --git a/CMakeLists.txt b/CMakeLists.txt
index e694dfc4..45813bac 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,6 +30,11 @@ if(NOT CMAKE_CXX_STANDARD)
     set(CMAKE_CXX_STANDARD_REQUIRED ON)
 endif()
 
+# make sure __cplusplus is defined under msvc
+if(MSVC)
+    string(APPEND CMAKE_CXX_FLAGS " /Zc:__cplusplus")
+endif()
+
 set(CMAKE_CXX_EXTENSIONS OFF)
 
 if(CMAKE_SYSTEM_NAME MATCHES "CYGWIN" OR CMAKE_SYSTEM_NAME MATCHES "MSYS")