diff --git a/src/os_win32.h b/src/os_win32.h
index 87555b7..5995e70 100644
--- a/src/os_win32.h
+++ b/src/os_win32.h
@@ -85,6 +85,10 @@
 # define COBJMACROS	// For OLE: Enable "friendlier" access to objects
 #endif
 #ifndef PROTO
+// Must include winsock2.h before windows.h since it conflicts with winsock.h
+// (included in windows.h).
+# include <winsock2.h>
+# include <ws2tcpip.h>
 # include <windows.h>
 
 // Weird: rpcndr.h defines "small" to "char", which causes trouble