diff --git a/reactos/dll/win32/wininet/internet.h b/reactos/dll/win32/wininet/internet.h
index bb694e91b3e..0dcf5a22ce6 100644
--- a/reactos/dll/win32/wininet/internet.h
+++ b/reactos/dll/win32/wininet/internet.h
@@ -52,6 +52,10 @@
 #define ioctlsocket ioctl
 #endif /* __MINGW32__ */
 
+/* ReactOS-specific definitions */
+#undef CP_UNIXCP
+#define CP_UNIXCP   CP_THREAD_ACP
+
 /* used for netconnection.c stuff */
 typedef struct
 {