diff --git a/src/components/KeyValueEditor.vue b/src/components/KeyValueEditor.vue
index f6be35726..b78c751a8 100644
--- a/src/components/KeyValueEditor.vue
+++ b/src/components/KeyValueEditor.vue
@@ -44,7 +44,7 @@ interface KeyValueObj {
 export default class KeyValueEditor extends Vue {
   @Prop({ required: false, default: '' }) private title!: string
   @Prop({ required: false, default: '100%' }) private maxHeight!: string
-  @Model('change', { type: Object }) private readonly value!: { [key: string]: string }
+  @Model('change', { type: Object }) private readonly value!: { [key: string]: string } | null
 
   private dataList: KeyValueObj[] = []
 
@@ -70,7 +70,7 @@ export default class KeyValueEditor extends Vue {
       this.handleInputChange()
     } else if (this.dataList.length === 1) {
       this.dataList = [{ key: '', value: '', checked: true }]
-      this.$emit('change', undefined)
+      this.$emit('change', null)
     }
   }
   private checkItem(index: number) {
@@ -79,7 +79,7 @@ export default class KeyValueEditor extends Vue {
   }
 
   private processObjToArry() {
-    if (this.value === undefined) {
+    if (this.value === undefined || this.value === null) {
       this.dataList = [{ key: '', value: '', checked: true }]
       return
     }
diff --git a/src/database/services/ConnectionService.ts b/src/database/services/ConnectionService.ts
index 3ef0d17a6..ca361a3b7 100644
--- a/src/database/services/ConnectionService.ts
+++ b/src/database/services/ConnectionService.ts
@@ -79,10 +79,13 @@ export default class ConnectionService {
         topicAliasMaximum,
         requestResponseInformation,
         requestProblemInformation,
-        userProperties,
         authenticationMethod,
         authenticationData,
       } = data.properties
+      let userProperties = null
+      if (data.properties.userProperties) {
+        userProperties = JSON.stringify(data.properties.userProperties)
+      }
       return {
         ...data,
         sessionExpiryInterval,
@@ -93,12 +96,12 @@ export default class ConnectionService {
         requestProblemInformation,
         authenticationMethod,
         authenticationData: authenticationData?.toString('utf8'),
-        userProperties: JSON.stringify(userProperties),
+        userProperties,
       }
     }
     return {
       ...data,
-    } as ConnectionEntity
+    }
   }
 
   // update connection's collection ID
@@ -178,6 +181,7 @@ export default class ConnectionService {
     data.parentId = queryModel.parentId
     // END FIXME
     const res: ConnectionModel = query ? this.deepMerge(queryModel, data) : data
+    // Will Message table
     if (res.will) {
       const {
         id,
@@ -206,10 +210,10 @@ export default class ConnectionService {
         res.will = await this.willRepository.save({
           id,
           ...data,
-        } as WillEntity)
+        })
       } else {
         // no will relation in database
-        res.will = await this.willRepository.save(data as WillEntity)
+        res.will = await this.willRepository.save(data)
       }
     } else {
       // no will relation in memory or database
@@ -221,6 +225,7 @@ export default class ConnectionService {
         lastWillRetain: false,
       })
     }
+    // Subscriptions table
     if (res.subscriptions && Array.isArray(res.subscriptions)) {
       const curSubs: SubscriptionEntity[] = await this.subscriptionRepository
         .createQueryBuilder('sub')
diff --git a/src/types/global.d.ts b/src/types/global.d.ts
index a8f1d0421..9b7d7afab 100644
--- a/src/types/global.d.ts
+++ b/src/types/global.d.ts
@@ -260,9 +260,9 @@ declare global {
     topicAliasMaximum?: number | null
     requestResponseInformation?: boolean | null
     requestProblemInformation?: boolean | null
-    userProperties?: Object
-    authenticationMethod?: string
-    authenticationData?: Buffer
+    userProperties?: Object | null
+    authenticationMethod?: string | null
+    authenticationData?: Buffer | null
   }
 
   interface PushOptions {