diff --git a/slirp/ip.h b/slirp/ip.h
index 83fc9cdfbf..243b6c8b24 100644
--- a/slirp/ip.h
+++ b/slirp/ip.h
@@ -177,7 +177,7 @@ struct	ip_timestamp {
 
 #define	IP_MSS		576		/* default maximum segment size */
 
-#if SIZEOF_CHAR_P == 4
+#if GLIB_SIZEOF_VOID_P == 4
 struct mbuf_ptr {
 	struct mbuf *mptr;
 	uint32_t dummy;
diff --git a/slirp/slirp_config.h b/slirp/slirp_config.h
index b2def6d20c..7147e0de04 100644
--- a/slirp/slirp_config.h
+++ b/slirp/slirp_config.h
@@ -10,6 +10,3 @@
  * Autoconf defined configuration options
  * You shouldn't need to touch any of these
  */
-
-/* Define to sizeof(char *) */
-#define SIZEOF_CHAR_P (HOST_LONG_BITS / 8)