diff --git a/ext/socket/ipsocket.c b/ext/socket/ipsocket.c
index efaca265d5..60776c16a2 100644
--- a/ext/socket/ipsocket.c
+++ b/ext/socket/ipsocket.c
@@ -593,7 +593,7 @@ init_fast_fallback_inetsock_internal(VALUE v)
         arg->getaddrinfo_shared->notify = hostname_resolution_notifier;
 
         arg->getaddrinfo_shared->node = arg->hostp ? ruby_strdup(arg->hostp) : NULL;
-        arg->getaddrinfo_shared->service = ruby_strdup(arg->portp);
+        arg->getaddrinfo_shared->service = arg->portp ? ruby_strdup(arg->portp) : NULL;
         arg->getaddrinfo_shared->refcount = arg->family_size + 1;
 
         for (int i = 0; i < arg->family_size; i++) {