diff --git a/Modules/socketmodule.h b/Modules/socketmodule.h
index fdb4e87..bce74c3 100644
--- a/Modules/socketmodule.h
+++ b/Modules/socketmodule.h
@@ -28,7 +28,7 @@
  * I use SIO_GET_MULTICAST_FILTER to detect a decent SDK.
  */
 # ifdef SIO_GET_MULTICAST_FILTER
-#  include <MSTcpIP.h> /* for SIO_RCVALL */
+#  include <mstcpip.h> /* for SIO_RCVALL */
 #  define HAVE_ADDRINFO
 #  define HAVE_SOCKADDR_STORAGE
 #  define HAVE_GETADDRINFO