diff --git a/deno.json b/deno.json
index f792084..b9f334d 100644
--- a/deno.json
+++ b/deno.json
@@ -1,6 +1,6 @@
 {
   "name": "@serve.zone/nupst",
-  "version": "4.0.4",
+  "version": "4.0.5",
   "exports": "./mod.ts",
   "tasks": {
     "dev": "deno run --allow-all mod.ts",
diff --git a/ts/migrations/migration-v3-to-v4.ts b/ts/migrations/migration-v3-to-v4.ts
index 30b3ed5..7faab71 100644
--- a/ts/migrations/migration-v3-to-v4.ts
+++ b/ts/migrations/migration-v3-to-v4.ts
@@ -44,17 +44,30 @@ export class MigrationV3ToV4 extends BaseMigration {
   readonly toVersion = '4.0';
 
   async shouldRun(config: any): Promise<boolean> {
-    // V3 format has upsList instead of upsDevices
-    return !!config.upsList && !config.upsDevices;
+    // V3 format has upsList OR has upsDevices with flat structure (host at top level)
+    if (config.upsList && !config.upsDevices) {
+      return true; // Classic v3 with upsList
+    }
+
+    // Check if upsDevices exists but has flat structure (v3 format)
+    if (config.upsDevices && config.upsDevices.length > 0) {
+      const firstDevice = config.upsDevices[0];
+      // V3 has host at top level, v4 has it nested in snmp object
+      return !!firstDevice.host && !firstDevice.snmp;
+    }
+
+    return false;
   }
 
   async migrate(config: any): Promise<any> {
     logger.info(`${this.getName()}: Migrating v3 config to v4 format...`);
-    logger.dim(`  - Renaming upsList → upsDevices`);
     logger.dim(`  - Restructuring UPS devices (flat → nested snmp config)`);
 
+    // Get devices from either upsList or upsDevices (for partially migrated configs)
+    const sourceDevices = config.upsList || config.upsDevices;
+
     // Transform each UPS device from v3 flat structure to v4 nested structure
-    const transformedDevices = config.upsList.map((device: any) => {
+    const transformedDevices = sourceDevices.map((device: any) => {
       // Build SNMP config object
       const snmpConfig: any = {
         host: device.host,