diff --git a/net/net.c b/net/net.c
index d21c2c7..76ba0b7 100644
--- a/net/net.c
+++ b/net/net.c
@@ -1105,6 +1105,7 @@
 
 static int net_client_init(QemuOpts *opts, bool is_netdev, Error **errp)
 {
+    gchar **substrings = NULL;
     void *object = NULL;
     Error *err = NULL;
     int ret = -1;
@@ -1120,28 +1121,33 @@
         const char *ip6_net = qemu_opt_get(opts, "ipv6-net");
 
         if (ip6_net) {
-            char buf[strlen(ip6_net) + 1];
+            char *prefix_addr;
+            unsigned long prefix_len = 64; /* Default 64bit prefix length. */
 
-            if (get_str_sep(buf, sizeof(buf), &ip6_net, '/') < 0) {
-                /* Default 64bit prefix length.  */
-                qemu_opt_set(opts, "ipv6-prefix", ip6_net, &error_abort);
-                qemu_opt_set_number(opts, "ipv6-prefixlen", 64, &error_abort);
-            } else {
+            substrings = g_strsplit(ip6_net, "/", 2);
+            if (!substrings || !substrings[0]) {
+                error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "ipv6-net",
+                           "a valid IPv6 prefix");
+                goto out;
+            }
+
+            prefix_addr = substrings[0];
+
+            if (substrings[1]) {
                 /* User-specified prefix length.  */
-                unsigned long len;
                 int err;
 
-                qemu_opt_set(opts, "ipv6-prefix", buf, &error_abort);
-                err = qemu_strtoul(ip6_net, NULL, 10, &len);
-
+                err = qemu_strtoul(substrings[1], NULL, 10, &prefix_len);
                 if (err) {
                     error_setg(errp, QERR_INVALID_PARAMETER_VALUE,
                                "ipv6-prefixlen", "a number");
                     goto out;
                 }
-
-                qemu_opt_set_number(opts, "ipv6-prefixlen", len, &error_abort);
             }
+
+            qemu_opt_set(opts, "ipv6-prefix", prefix_addr, &error_abort);
+            qemu_opt_set_number(opts, "ipv6-prefixlen", prefix_len,
+                                &error_abort);
             qemu_opt_unset(opts, "ipv6-net");
         }
     }
@@ -1164,6 +1170,7 @@
 
 out:
     error_propagate(errp, err);
+    g_strfreev(substrings);
     visit_free(v);
     return ret;
 }