diff --git a/changes/ticket40073 b/changes/ticket40073
new file mode 100644
index 0000000000..30b028c042
--- /dev/null
+++ b/changes/ticket40073
@@ -0,0 +1,3 @@
+  o Minor bugfixes (relay configuration, crash):
+    - Avoid a fatal assert() when failing to create a listener connection for an
+      address that was in use. Fixes bug 40073; bugfix on 0.3.5.1-alpha.
diff --git a/src/core/mainloop/connection.c b/src/core/mainloop/connection.c
index 57b48d49f3..268c7a70be 100644
--- a/src/core/mainloop/connection.c
+++ b/src/core/mainloop/connection.c
@@ -3043,7 +3043,14 @@ retry_all_listeners(smartlist_t *new_conns, int close_all_noncontrol)
                                                   &skip, &addr_in_use);
     }
 
-    tor_assert(new_conn);
+    /* There are many reasons why we can't open a new listener port so in case
+     * we hit those, bail early so tor can stop. */
+    if (!new_conn) {
+      log_warn(LD_NET, "Unable to create listener port: %s:%d",
+               fmt_addr(&r->new_port->addr), r->new_port->port);
+      retval = -1;
+      break;
+    }
 
     smartlist_add(new_conns, new_conn);