diff --git a/reactos/drivers/network/dd/pcnet/pcnet.h b/reactos/drivers/network/dd/pcnet/pcnet.h
index be9ae0ca6dc..27e51f02d44 100644
--- a/reactos/drivers/network/dd/pcnet/pcnet.h
+++ b/reactos/drivers/network/dd/pcnet/pcnet.h
@@ -145,6 +145,10 @@ MiGetMediaState(PADAPTER Adapter);
 #define BREAKPOINT
 #endif
 
+#ifndef TAG
+#define TAG(A, B, C, D) (ULONG)(((A)<<0) + ((B)<<8) + ((C)<<16) + ((D)<<24))
+#endif
+
 /* memory pool tag */
 #define PCNET_TAG TAG('P', 'c', 'N', 't')