diff --git a/web/app/cad/craft/craftPlugin.js b/web/app/cad/craft/craftPlugin.js
index d44aaaa1..4f6fbe7c 100644
--- a/web/app/cad/craft/craftPlugin.js
+++ b/web/app/cad/craft/craftPlugin.js
@@ -4,6 +4,7 @@ import {MShell} from '../model/mshell';
 import {MDatum} from '../model/mdatum';
 import materializeParams from './materializeParams';
 import CadError from '../../utils/errors';
+import {MObjectIdGenerator} from '../model/mobject';
 
 export function activate({streams, services}) {
 
@@ -87,8 +88,7 @@ export function activate({streams, services}) {
     if (isAdditiveChange(prev, curr)) {
       beginIndex = prev.pointer + 1;
     } else {
-      MShell.ID_COUNTER = 0;
-      MDatum.ID_COUNTER = 0;
+      MObjectIdGenerator.reset();
       beginIndex = 0;
       streams.craft.models.next([]);
     }
diff --git a/web/app/cad/model/mdatum.js b/web/app/cad/model/mdatum.js
index dc540360..8dc1cdc0 100644
--- a/web/app/cad/model/mdatum.js
+++ b/web/app/cad/model/mdatum.js
@@ -1,12 +1,11 @@
-import {MObject} from './mobject';
+import {MObject, MObjectIdGenerator} from './mobject';
 
 export class MDatum extends MObject {
 
   static TYPE = 'datum';
-  static ID_COUNTER = 0; // TODO: reset the counter
   
   constructor(csys) {
-    super(MDatum.TYPE, 'D:' + (MDatum.ID_COUNTER++));
+    super(MDatum.TYPE, 'D:' + MObjectIdGenerator.next(MDatum.TYPE));
     this.csys = csys;
     this.xAxis = new MDatumAxis(this.id + '/X', this.csys.origin, this.csys.x);
     this.yAxis = new MDatumAxis(this.id + '/Y', this.csys.origin, this.csys.y);
diff --git a/web/app/cad/model/mobject.js b/web/app/cad/model/mobject.js
index d9873930..14c83040 100644
--- a/web/app/cad/model/mobject.js
+++ b/web/app/cad/model/mobject.js
@@ -10,6 +10,15 @@ export class MObject {
     this.TYPE = TYPE;
     this.id = id;
   }
-  
 }
 
+const ID_REGISTRY = new Map();
+
+export const MObjectIdGenerator = {
+  next: entityType => {
+    const id = ID_REGISTRY.get(entityType) || 0;
+    ID_REGISTRY.set(entityType, id + 1);
+    return id;
+  },
+  reset: () => ID_REGISTRY.clear()
+};
diff --git a/web/app/cad/model/mshell.js b/web/app/cad/model/mshell.js
index 8d3e5f1c..65f481ce 100644
--- a/web/app/cad/model/mshell.js
+++ b/web/app/cad/model/mshell.js
@@ -1,4 +1,4 @@
-import {MObject} from './mobject';
+import {MObject, MObjectIdGenerator} from './mobject';
 import {MBrepFace, MFace} from './mface';
 import {MEdge} from './medge';
 import {MVertex} from './mvertex';
@@ -8,10 +8,8 @@ export class MShell extends MObject {
 
   static TYPE = 'shell';
 
-  static ID_COUNTER = 0;
-
   constructor() {
-    super(MShell.TYPE, 'S:' + (MShell.ID_COUNTER++))  
+    super(MShell.TYPE, 'S:' + MObjectIdGenerator.next(MShell.TYPE))  
   }
   
   shell;