diff --git a/mongoose.c b/mongoose.c
index d60c4847..8f4379ba 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -4209,6 +4209,7 @@ static void mg_socks_if_free(struct mg_iface *iface) {
   LOG(LL_DEBUG, ("%p", iface));
   if (d != NULL) {
     socks_if_disband(d);
+    mbuf_free(&d->tmp);
     MG_FREE(d->proxy_addr);
     MG_FREE(d);
     iface->data = NULL;