--- a/src/include/lspclient.h
+++ b/src/include/lspclient.h
@@ -29,6 +29,9 @@
 #define LSPCLIENT_H
 
 #ifdef _WIN32
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
 #include <windows.h>
 #include <stdio.h>
 #include <tchar.h>
