diff --git a/packages/mindplot/src/components/Relationship.ts b/packages/mindplot/src/components/Relationship.ts
index a3abb457..69397b36 100644
--- a/packages/mindplot/src/components/Relationship.ts
+++ b/packages/mindplot/src/components/Relationship.ts
@@ -38,7 +38,7 @@ class Relationship extends ConnectionLine {
 
   private _endArrow: Arrow;
 
-  private _controlPointControllerListener: any;
+  private _controlPointControllerListener;
 
   private _showStartArrow: Arrow;
 
diff --git a/packages/mindplot/src/components/Topic.ts b/packages/mindplot/src/components/Topic.ts
index 3e5f6989..83a41aea 100644
--- a/packages/mindplot/src/components/Topic.ts
+++ b/packages/mindplot/src/components/Topic.ts
@@ -1058,7 +1058,7 @@ abstract class Topic extends NodeGraph {
     }
   }
 
-  setSize(size: SizeType, force: boolean): void {
+  setSize(size: SizeType, force?: boolean): void {
     $assert(size, 'size can not be null');
     $assert($defined(size.width), 'size seem not to be a valid element');
     const roundedSize = {
diff --git a/packages/mindplot/src/components/commands/DeleteCommand.ts b/packages/mindplot/src/components/commands/DeleteCommand.ts
index e28b002b..c8019603 100644
--- a/packages/mindplot/src/components/commands/DeleteCommand.ts
+++ b/packages/mindplot/src/components/commands/DeleteCommand.ts
@@ -20,6 +20,7 @@ import Command from '../Command';
 import CommandContext from '../CommandContext';
 import NodeModel from '../model/NodeModel';
 import RelationshipModel from '../model/RelationshipModel';
+import Relationship from '../Relationship';
 import Topic from '../Topic';
 
 class DeleteCommand extends Command {
@@ -159,13 +160,16 @@ class DeleteCommand extends Command {
     return result;
   }
 
-  _collectInDepthRelationships(topic: Topic) {
+  private _collectInDepthRelationships(topic: Topic): Relationship[] {
     let result = [];
     result = result.concat(topic.getRelationships());
 
     const children = topic.getChildren();
-    const rels = children.map(((t) => this._collectInDepthRelationships(t)));
-    result = result.concat(rels.flat());
+    const rels: (Relationship[])[] = children
+      .map(((t: Topic) => this._collectInDepthRelationships(t)));
+
+    // flatten and concact
+    result = result.concat(([].concat(...rels)));
 
     if (result.length > 0) {
       // Filter for unique ...
diff --git a/packages/mindplot/tsconfig.json b/packages/mindplot/tsconfig.json
index c342a977..379d8747 100644
--- a/packages/mindplot/tsconfig.json
+++ b/packages/mindplot/tsconfig.json
@@ -5,7 +5,7 @@
     "noImplicitAny": false,
     "module": "amd",
     "moduleResolution": "node",
-    "target": "es6",
+    "target": "ES2020",
     "allowJs": true,
     "esModuleInterop": true,
     "declaration": true,