diff --git a/sys/netpfil/pf/if_pfsync.c b/sys/netpfil/pf/if_pfsync.c
index 66bc99df2af..de69ecbb098 100644
--- a/sys/netpfil/pf/if_pfsync.c
+++ b/sys/netpfil/pf/if_pfsync.c
@@ -546,6 +546,9 @@ pfsync_state_import(union pfsync_state_union *sp, int flags, int msg_version)
 
 	PF_RULES_RASSERT();
 
+	if (strnlen(sp->pfs_1301.ifname, IFNAMSIZ) == IFNAMSIZ)
+		return (EINVAL);
+
 	if (sp->pfs_1301.creatorid == 0) {
 		if (V_pf_status.debug >= PF_DEBUG_MISC)
 			printf("%s: invalid creator id: %08x\n", __func__,
diff --git a/tests/sys/netpfil/pf/ioctl/validation.c b/tests/sys/netpfil/pf/ioctl/validation.c
index a619cfdff2e..bb060e22f3a 100644
--- a/tests/sys/netpfil/pf/ioctl/validation.c
+++ b/tests/sys/netpfil/pf/ioctl/validation.c
@@ -981,6 +981,30 @@ ATF_TC_CLEANUP(natlook, tc)
 	COMMON_CLEANUP();
 }
 
+ATF_TC_WITH_CLEANUP(addstate);
+ATF_TC_HEAD(addstate, tc)
+{
+	atf_tc_set_md_var(tc, "require.user", "root");
+	atf_tc_set_md_var(tc, "require.kmods", "pfsync");
+}
+
+ATF_TC_BODY(addstate, tc)
+{
+	struct pfioc_state st;
+
+	COMMON_HEAD();
+
+	memset(&st, 'a', sizeof(st));
+	st.state.timeout = PFTM_TCP_FIRST_PACKET;
+
+	ATF_CHECK_ERRNO(EINVAL, ioctl(dev, DIOCADDSTATE, &st) == -1);
+}
+
+ATF_TC_CLEANUP(addstate, tc)
+{
+	COMMON_CLEANUP();
+}
+
 ATF_TP_ADD_TCS(tp)
 {
 	ATF_TP_ADD_TC(tp, addtables);
@@ -1007,6 +1031,7 @@ ATF_TP_ADD_TCS(tp)
 	ATF_TP_ADD_TC(tp, rpool_mtx);
 	ATF_TP_ADD_TC(tp, rpool_mtx2);
 	ATF_TP_ADD_TC(tp, natlook);
+	ATF_TP_ADD_TC(tp, addstate);
 
 	return (atf_no_error());
 }