diff -rupN eigen-eigen-bdd17ee3b1b3/cmake/EigenDetermineOSVersion.cmake eigen-eigen-bdd17ee3b1b3-new/cmake/EigenDetermineOSVersion.cmake
--- eigen-eigen-bdd17ee3b1b3/cmake/EigenDetermineOSVersion.cmake	2015-06-16 11:53:07.000000000 +0200
+++ eigen-eigen-bdd17ee3b1b3-new/cmake/EigenDetermineOSVersion.cmake	2015-06-16 18:09:35.263198608 +0200
@@ -26,7 +26,7 @@ function(DetermineShortWindowsName WIN_V
 endfunction()
 
 function(DetermineOSVersion OS_VERSION)
-  if (WIN32)
+  if (WIN32 AND NOT MINGW)
     file (TO_NATIVE_PATH "$ENV{COMSPEC}" SHELL)
     exec_program( ${SHELL} ARGS "/c" "ver" OUTPUT_VARIABLE ver_output)