diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1bd293c6b..e66c25ea1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -157,6 +157,7 @@ else(BOOTSTRAP_WXWIDGETS AND NOT EXISTS ${WXCONFIG})
 #
 if(MINGW)
     message(STATUS "System is MinGW.")
+    add_definitions(-DWIN32=1)
     # Default to static build of portaudio until I can figure out why the
     # shared DLL doesn't work.
     set(USE_STATIC_PORTAUDIO TRUE)