diff --git a/mongoose.c b/mongoose.c
index f1bcd660..0e249e4c 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -3562,6 +3562,7 @@ struct mg_connection *mg_listen(struct mg_mgr *mgr, const char *url,
   } else if (!mg_open_listener(c, url)) {
     MG_ERROR(("Failed: %s, errno %d", url, errno));
     free(c);
+    c = NULL;
   } else {
     c->is_listening = 1;
     c->is_udp = strncmp(url, "udp:", 4) == 0;
diff --git a/src/net.c b/src/net.c
index d2333cd5..7cefd42e 100644
--- a/src/net.c
+++ b/src/net.c
@@ -194,6 +194,7 @@ struct mg_connection *mg_listen(struct mg_mgr *mgr, const char *url,
   } else if (!mg_open_listener(c, url)) {
     MG_ERROR(("Failed: %s, errno %d", url, errno));
     free(c);
+    c = NULL;
   } else {
     c->is_listening = 1;
     c->is_udp = strncmp(url, "udp:", 4) == 0;
diff --git a/test/unit_test.c b/test/unit_test.c
index 11301434..fa64b4f8 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -663,9 +663,10 @@ static void test_http_server(void) {
     ASSERT(mg_http_etag(etag, sizeof(etag), size, mtime) == etag);
     ASSERT(fetch(&mgr, buf, url, "GET /a.txt HTTP/1.0\nIf-None-Match: %s\n\n",
                  etag) == 304);
-    mg_http_parse(buf, strlen(buf), &hm);
-    ASSERT(mg_http_get_header(&hm, "A") != NULL);
-    ASSERT(mg_strcmp(*mg_http_get_header(&hm, "A"), mg_str("B")) == 0);
+    ASSERT(mg_http_parse(buf, strlen(buf), &hm) > 0);
+    MG_INFO(("%s", buf));
+    ASSERT(mg_http_get_header(&hm, "C") != NULL);
+    ASSERT(mg_strcmp(*mg_http_get_header(&hm, "C"), mg_str("D")) == 0);
   }
 
   // Text mime type override
@@ -1607,14 +1608,14 @@ static void test_http_upload(void) {
   const char *s2 = "ok (8 foo\nbar\n)\n";
 
   mg_mgr_init(&mgr);
-  mg_http_listen(&mgr, url, us, &del);
+  mg_http_listen(&mgr, url, us, (void *) &del);
 
-  mg_http_connect(&mgr, url, uc, &s1);
+  mg_http_connect(&mgr, url, uc, (void *) &s1);
   for (i = 0; i < 20; i++) mg_mgr_poll(&mgr, 5);
   ASSERT(s1 == NULL);
 
   del = 0;
-  mg_http_connect(&mgr, url, uc, &s2);
+  mg_http_connect(&mgr, url, uc, (void *) &s2);
   for (i = 0; i < 20; i++) mg_mgr_poll(&mgr, 5);
   ASSERT(s2 == NULL);
 
@@ -1721,6 +1722,16 @@ static void test_http_chunked(void) {
   ASSERT(mgr.conns == NULL);
 }
 
+static void test_invalid_listen_addr(void) {
+  struct mg_mgr mgr;
+  struct mg_connection *c;
+  mg_mgr_init(&mgr);
+  c = mg_http_listen(&mgr, "invalid:31:14", eh1, NULL);
+  ASSERT(c == NULL);
+  mg_mgr_free(&mgr);
+  ASSERT(mgr.conns == NULL);
+}
+
 static void test_multipart(void) {
   struct mg_http_part part;
   size_t ofs;
@@ -1989,6 +2000,7 @@ int main(void) {
   test_packed();
   test_crc32();
   test_multipart();
+  test_invalid_listen_addr();
   test_http_chunked();
   test_http_upload();
   test_http_parse();