diff --git a/reactos/dll/win32/urlmon/urlmon.rbuild b/reactos/dll/win32/urlmon/urlmon.rbuild
index c8c75863db4..c904c5726a0 100644
--- a/reactos/dll/win32/urlmon/urlmon.rbuild
+++ b/reactos/dll/win32/urlmon/urlmon.rbuild
@@ -49,7 +49,7 @@
 	<define name="PROXY_DELEGATION"/>
 	<define name="REGISTER_PROXY_DLL"/>
 	<define name="_URLMON_"/>
-	<define name="PROXY_CLSID_IS">{0x79EAC9F1,0xBAF9,0x11CE,{0x8C,0x82,0x00,0xAA,0x00,0x4B,0xA9,0x0B}}</define>
+	<define name="PROXY_CLSID_IS">"{0x79EAC9F1,0xBAF9,0x11CE,{0x8C,0x82,0x00,0xAA,0x00,0x4B,0xA9,0x0B}}"</define>
 	<file>urlmon_urlmon.idl</file>
 </module>
 </group>