diff --git a/modules/core/graph.js b/modules/core/graph.js
index 93da4efa6..d83745aaa 100644
--- a/modules/core/graph.js
+++ b/modules/core/graph.js
@@ -1,5 +1,4 @@
 import _difference from 'lodash-es/difference';
-import _includes from 'lodash-es/includes';
 
 import { debug } from '../index';
 
@@ -65,36 +64,34 @@ coreGraph.prototype = {
     parentWays: function(entity) {
         var parents = this._parentWays[entity.id];
         var result = [];
-
         if (parents) {
-            for (var i = 0; i < parents.length; i++) {
-                result.push(this.entity(parents[i]));
-            }
+            parents.forEach(function(id) {
+                result.push(this.entity(id));
+            }, this);
         }
         return result;
     },
 
 
     isPoi: function(entity) {
-        var parentWays = this._parentWays[entity.id];
-        return !parentWays || parentWays.length === 0;
+        var parents = this._parentWays[entity.id];
+        return !parents || parents.size === 0;
     },
 
 
     isShared: function(entity) {
-        var parentWays = this._parentWays[entity.id];
-        return parentWays && parentWays.length > 1;
+        var parents = this._parentWays[entity.id];
+        return parents && parents.size > 1;
     },
 
 
     parentRelations: function(entity) {
         var parents = this._parentRels[entity.id];
         var result = [];
-
         if (parents) {
-            for (var i = 0; i < parents.length; i++) {
-                result.push(this.entity(parents[i]));
-            }
+            parents.forEach(function(id) {
+                result.push(this.entity(id));
+            }, this);
         }
         return result;
     },
@@ -171,33 +168,26 @@ coreGraph.prototype = {
 
     _updateRebased: function() {
         var base = this.base();
-        var i, k, child, id, keys;
 
-        keys = Object.keys(this._parentWays);
-        for (i = 0; i < keys.length; i++) {
-            child = keys[i];
+        Object.keys(this._parentWays).forEach(function(child) {
             if (base.parentWays[child]) {
-                for (k = 0; k < base.parentWays[child].length; k++) {
-                    id = base.parentWays[child][k];
-                    if (!this.entities.hasOwnProperty(id) && !_includes(this._parentWays[child], id)) {
-                        this._parentWays[child].push(id);
+                base.parentWays[child].forEach(function(id) {
+                    if (!this.entities.hasOwnProperty(id)) {
+                        this._parentWays[child].add(id);
                     }
-                }
+                }, this);
             }
-        }
+        }, this);
 
-        keys = Object.keys(this._parentRels);
-        for (i = 0; i < keys.length; i++) {
-            child = keys[i];
+        Object.keys(this._parentRels).forEach(function(child) {
             if (base.parentRels[child]) {
-                for (k = 0; k < base.parentRels[child].length; k++) {
-                    id = base.parentRels[child][k];
-                    if (!this.entities.hasOwnProperty(id) && !_includes(this._parentRels[child], id)) {
-                        this._parentRels[child].push(id);
+                base.parentRels[child].forEach(function(id) {
+                    if (!this.entities.hasOwnProperty(id)) {
+                        this._parentRels[child].add(id);
                     }
-                }
+                }, this);
             }
-        }
+        }, this);
 
         this.transients = {};
 
@@ -212,7 +202,7 @@ coreGraph.prototype = {
         parentRels = parentRels || this._parentRels;
 
         var type = entity && entity.type || oldentity && oldentity.type;
-        var removed, added, ways, rels, i;
+        var removed, added, i;
 
         if (type === 'way') {   // Update parentWays
             if (oldentity && entity) {
@@ -226,14 +216,14 @@ coreGraph.prototype = {
                 added = entity.nodes;
             }
             for (i = 0; i < removed.length; i++) {
-                parentWays[removed[i]] = (parentWays[removed[i]] || [])
-                    .filter(function(id) { return id !== oldentity.id; });
+                // make a copy of prototype property, store as own property, and update..
+                parentWays[removed[i]] = new Set(parentWays[removed[i]]);
+                parentWays[removed[i]].delete(oldentity.id);
             }
             for (i = 0; i < added.length; i++) {
-                ways = (parentWays[added[i]] || [])
-                    .filter(function(id) { return id !== entity.id; });
-                ways.push(entity.id);
-                parentWays[added[i]] = ways;
+                // make a copy of prototype property, store as own property, and update..
+                parentWays[added[i]] = new Set(parentWays[added[i]]);
+                parentWays[added[i]].add(entity.id);
             }
 
         } else if (type === 'relation') {   // Update parentRels
@@ -248,14 +238,14 @@ coreGraph.prototype = {
                 added = entity.members;
             }
             for (i = 0; i < removed.length; i++) {
-                parentRels[removed[i].id] = (parentRels[removed[i].id] || [])
-                    .filter(function(id) { return id !== oldentity.id; });
+                // make a copy of prototype property, store as own property, and update..
+                parentRels[removed[i].id] = new Set(parentRels[removed[i].id]);
+                parentRels[removed[i].id].delete(oldentity.id);
             }
             for (i = 0; i < added.length; i++) {
-                rels = (parentRels[added[i].id] || [])
-                    .filter(function(id) { return id !== entity.id; });
-                rels.push(entity.id);
-                parentRels[added[i].id] = rels;
+                // make a copy of prototype property, store as own property, and update..
+                parentRels[added[i].id] = new Set(parentRels[added[i].id]);
+                parentRels[added[i].id].add(entity.id);
             }
         }
     },