diff --git a/src/main/resources/db/migration/V5__posture_device_id_nullable.sql b/src/main/resources/db/migration/V5__posture_device_id_nullable.sql
new file mode 100644
index 0000000..7b543fd
--- /dev/null
+++ b/src/main/resources/db/migration/V5__posture_device_id_nullable.sql
@@ -0,0 +1,3 @@
+-- device_id retained its NOT NULL constraint after the PK was dropped in V4.
+-- Make it nullable so agents that don't send a numeric deviceId can persist.
+ALTER TABLE device_security_posture ALTER COLUMN device_id DROP NOT NULL;