diff --git a/lib/towerops/device_profiles.ex b/lib/towerops/device_profiles.ex
index ebce23a6..fbb8a847 100644
--- a/lib/towerops/device_profiles.ex
+++ b/lib/towerops/device_profiles.ex
@@ -170,12 +170,17 @@ defmodule Towerops.DeviceProfiles do
   defp match_rule?(%DetectionRule{rule_type: "sysObjectID"} = rule, system_info) do
     sys_object_id = Map.get(system_info, :sys_object_id, "")
 
+    # Normalize OID - prepend dot if not present for pattern matching
+    # LibreNMS uses ".1.3.6.1..." format, SNMP returns "1.3.6.1..." format
+    normalized_oid = if String.starts_with?(sys_object_id, "."), do: sys_object_id, else: "." <> sys_object_id
+
     cond do
       rule.pattern && rule.pattern != "" ->
-        String.contains?(sys_object_id, rule.pattern)
+        String.starts_with?(normalized_oid, rule.pattern)
 
       rule.value && rule.value != "" ->
-        sys_object_id == rule.value
+        normalized_value = if String.starts_with?(rule.value, "."), do: rule.value, else: "." <> rule.value
+        normalized_oid == normalized_value
 
       true ->
         false