diff --git a/net/slirp.c b/net/slirp.c
index dfc72cfc2e..a7802ddbcc 100644
--- a/net/slirp.c
+++ b/net/slirp.c
@@ -140,6 +140,10 @@ static NetClientInfo net_slirp_info = {
     .cleanup = net_slirp_cleanup,
 };
 
+static const SlirpCb slirp_cb = {
+    .output = net_slirp_output,
+};
+
 static int net_slirp_init(NetClientState *peer, const char *model,
                           const char *name, int restricted,
                           bool ipv4, const char *vnetwork, const char *vhost,
@@ -379,7 +383,7 @@ static int net_slirp_init(NetClientState *peer, const char *model,
                           vhostname, tftp_server_name,
                           tftp_export, bootfile, dhcp,
                           dns, ip6_dns, dnssearch, vdomainname,
-                          net_slirp_output, s);
+                          &slirp_cb, s);
     QTAILQ_INSERT_TAIL(&slirp_stacks, s, entry);
 
     for (config = slirp_configs; config; config = config->next) {
diff --git a/slirp/libslirp.h b/slirp/libslirp.h
index 04b6db9f49..a5d1b27b5e 100644
--- a/slirp/libslirp.h
+++ b/slirp/libslirp.h
@@ -5,7 +5,16 @@
 
 typedef struct Slirp Slirp;
 
-typedef void (*slirp_output)(void *opaque, const uint8_t *pkt, int pkt_len);
+/*
+ * Callbacks from slirp
+ *
+ * The opaque parameter comes from the opaque parameter given to slirp_init().
+ */
+typedef struct SlirpCb {
+    /* Send an ethernet frame to the guest network.  */
+    void (*output)(void *opaque, const uint8_t *pkt, int pkt_len);
+} SlirpCb;
+
 
 Slirp *slirp_init(int restricted, bool in_enabled, struct in_addr vnetwork,
                   struct in_addr vnetmask, struct in_addr vhost,
@@ -17,7 +26,7 @@ Slirp *slirp_init(int restricted, bool in_enabled, struct in_addr vnetwork,
                   struct in_addr vdhcp_start, struct in_addr vnameserver,
                   struct in6_addr vnameserver6, const char **vdnssearch,
                   const char *vdomainname,
-                  slirp_output output,
+                  const SlirpCb *callbacks,
                   void *opaque);
 void slirp_cleanup(Slirp *slirp);
 
diff --git a/slirp/ncsi.c b/slirp/ncsi.c
index d7701f7785..10decfb5ef 100644
--- a/slirp/ncsi.c
+++ b/slirp/ncsi.c
@@ -163,5 +163,5 @@ void ncsi_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
     *pchecksum = htonl(checksum);
     ncsi_rsp_len += 4;
 
-    slirp->output(slirp->opaque, ncsi_reply, ETH_HLEN + ncsi_rsp_len);
+    slirp->cb->output(slirp->opaque, ncsi_reply, ETH_HLEN + ncsi_rsp_len);
 }
diff --git a/slirp/slirp.c b/slirp/slirp.c
index 0e4ade3e4a..7213915bf3 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -288,14 +288,14 @@ Slirp *slirp_init(int restricted, bool in_enabled, struct in_addr vnetwork,
                   struct in_addr vdhcp_start, struct in_addr vnameserver,
                   struct in6_addr vnameserver6, const char **vdnssearch,
                   const char *vdomainname,
-                  slirp_output output,
+                  const SlirpCb *callbacks,
                   void *opaque)
 {
     Slirp *slirp = g_malloc0(sizeof(Slirp));
 
     slirp_init_once();
 
-    slirp->output = output;
+    slirp->cb = callbacks;
     slirp->grand = g_rand_new();
     slirp->restricted = restricted;
 
@@ -843,7 +843,7 @@ static void arp_input(Slirp *slirp, const uint8_t *pkt, int pkt_len)
             rah->ar_sip = ah->ar_tip;
             memcpy(rah->ar_tha, ah->ar_sha, ETH_ALEN);
             rah->ar_tip = ah->ar_sip;
-            slirp->output(slirp->opaque, arp_reply, sizeof(arp_reply));
+            slirp->cb->output(slirp->opaque, arp_reply, sizeof(arp_reply));
         }
         break;
     case ARPOP_REPLY:
@@ -943,7 +943,7 @@ static int if_encap4(Slirp *slirp, struct mbuf *ifm, struct ethhdr *eh,
             /* target IP */
             rah->ar_tip = iph->ip_dst.s_addr;
             slirp->client_ipaddr = iph->ip_dst;
-            slirp->output(slirp->opaque, arp_req, sizeof(arp_req));
+            slirp->cb->output(slirp->opaque, arp_req, sizeof(arp_req));
             ifm->resolution_requested = true;
 
             /* Expire request and drop outgoing packet after 1 second */
@@ -1029,7 +1029,7 @@ int if_encap(Slirp *slirp, struct mbuf *ifm)
                 eh->h_dest[0], eh->h_dest[1], eh->h_dest[2],
                 eh->h_dest[3], eh->h_dest[4], eh->h_dest[5]));
     memcpy(buf + sizeof(struct ethhdr), ifm->m_data, ifm->m_len);
-    slirp->output(slirp->opaque, buf, ifm->m_len + ETH_HLEN);
+    slirp->cb->output(slirp->opaque, buf, ifm->m_len + ETH_HLEN);
     return 1;
 }
 
diff --git a/slirp/slirp.h b/slirp/slirp.h
index de299aa36c..f7c087456a 100644
--- a/slirp/slirp.h
+++ b/slirp/slirp.h
@@ -220,7 +220,7 @@ struct Slirp {
     GRand *grand;
     QEMUTimer *ra_timer;
 
-    slirp_output output;
+    const SlirpCb *cb;
     void *opaque;
 };
 
