diff --git a/ItemTracked.js b/ItemTracked.js
index c1e78b6..5da4f87 100644
--- a/ItemTracked.js
+++ b/ItemTracked.js
@@ -12,6 +12,9 @@ var computeVelocityVector = require('./utils').computeVelocityVector
 //   "name": "car"
 // }
 
+/** The maximum length of the item history. */
+exports.ITEM_HISTORY_MAX_LENGTH = 15;
+
 // Use a simple incremental unique id for the display
 var idDisplay = 0;
 
@@ -48,6 +51,9 @@ exports.ItemTracked = function(properties, frameNb, unMatchedFramesTolerance, fa
     h: properties.h,
     confidence: properties.confidence
   });
+  if(itemTracked.itemHistory.length >= exports.ITEM_HISTORY_MAX_LENGTH) {
+    itemTracked.itemHistory.shift();
+  }
   itemTracked.velocity = {
     dx: 0,
     dy: 0
@@ -79,6 +85,9 @@ exports.ItemTracked = function(properties, frameNb, unMatchedFramesTolerance, fa
       h: this.h,
       confidence: this.confidence
     });
+    if(itemTracked.itemHistory.length >= exports.ITEM_HISTORY_MAX_LENGTH) {
+      itemTracked.itemHistory.shift();
+    }
     this.name = properties.name;
     if(this.nameCount[properties.name]) {
       this.nameCount[properties.name]++;
@@ -124,6 +133,9 @@ exports.ItemTracked = function(properties, frameNb, unMatchedFramesTolerance, fa
       h: this.h,
       confidence: this.confidence
     });
+    if(itemTracked.itemHistory.length >= exports.ITEM_HISTORY_MAX_LENGTH) {
+      itemTracked.itemHistory.shift();
+    }
     this.x = this.x + this.velocity.dx
     this.y = this.y + this.velocity.dy
   }
@@ -142,11 +154,18 @@ exports.ItemTracked = function(properties, frameNb, unMatchedFramesTolerance, fa
   }
   // Velocity vector based on the last 15 frames
   itemTracked.updateVelocityVector = function() {
-    var AVERAGE_NBFRAME = 15;
-    if(this.itemHistory.length <= AVERAGE_NBFRAME) {
-      return computeVelocityVector(this.itemHistory[0], this.itemHistory[this.itemHistory.length - 1], this.itemHistory.length);
+    if(exports.ITEM_HISTORY_MAX_LENGTH <= 2) {
+      return { dx: undefined, dy: undefined, }
+    }
+
+    if(this.itemHistory.length <= exports.ITEM_HISTORY_MAX_LENGTH) {
+      const start = this.itemHistory[0];
+      const end = this.itemHistory[this.itemHistory.length - 1];
+      return computeVelocityVector(start, end, this.itemHistory.length);
     } else {
-      return computeVelocityVector(this.itemHistory[this.itemHistory.length - AVERAGE_NBFRAME], this.itemHistory[this.itemHistory.length - 1], AVERAGE_NBFRAME);
+      const start = this.itemHistory[this.itemHistory.length - exports.ITEM_HISTORY_MAX_LENGTH];
+      const end = this.itemHistory[this.itemHistory.length - 1];
+      return computeVelocityVector(start, end, exports.ITEM_HISTORY_MAX_LENGTH);
     }
   }
 
diff --git a/package-lock.json b/package-lock.json
index e6a2ded..4d6e45b 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "node-moving-things-tracker",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "lockfileVersion": 2,
   "requires": true,
   "packages": {
     "": {
       "name": "node-moving-things-tracker",
-      "version": "0.9.0",
+      "version": "0.9.1",
       "license": "MIT",
       "dependencies": {
         "lodash.isequal": "^4.5.0",
diff --git a/package.json b/package.json
index 9c08763..200740e 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "node-moving-things-tracker",
-  "version": "0.9.0",
+  "version": "0.9.1",
   "description": "Tracker by detections in javascript for node.js / browsers",
   "url": "https://github.com/opendatacam/node-moving-things-tracker",
   "main": "main.js",
diff --git a/spec/ItemTracked.spec.js b/spec/ItemTracked.spec.js
index 3044bd3..3ad628a 100644
--- a/spec/ItemTracked.spec.js
+++ b/spec/ItemTracked.spec.js
@@ -1,30 +1,54 @@
 const ItemTracked = require('../ItemTracked');
 
 describe("ItemTracked", function () {
+  const properties = {
+    x: null,
+    y: null,
+    w: null,
+    h: null,
+    name: "dummy",
+    confidence: null
+  };
+
   describe("idDisplay", function () {
-    const properties = {
-        x: null,
-        y: null,
-        w: null,
-        h: null,
-        name: "dummy",
-        confidence: null
-    };
     const item1 = ItemTracked.ItemTracked(properties);
     const item2 = ItemTracked.ItemTracked(properties);
 
-    it('starts at 0', function() {
-        expect(item1.idDisplay).toBe(0);
+    it('starts at 0', function () {
+      expect(item1.idDisplay).toBe(0);
     });
 
-    it('icrements IDs', function() {
+    it('icrements IDs', function () {
       expect(item1.idDisplay).toBeLessThan(item2.idDisplay);
     });
 
-    it('resets IDs', function() {
-        ItemTracked.reset();
-        const item3 = ItemTracked.ItemTracked(properties);
-        expect(item3.idDisplay).toBe(0);
+    it('resets IDs', function () {
+      ItemTracked.reset();
+      const item3 = ItemTracked.ItemTracked(properties);
+      expect(item3.idDisplay).toBe(0);
+    });
+  });
+
+  describe('itemHistory', () => {
+    it('stops at max length', () => {
+      const item1 = ItemTracked.ItemTracked(properties);
+      for (var i = 0; i < ItemTracked.ITEM_HISTORY_MAX_LENGTH + 2; i++) {
+        item1.update(properties, i);
+        expect(item1.itemHistory.length).toBeLessThanOrEqual(ItemTracked.ITEM_HISTORY_MAX_LENGTH);
+      }
+    });
+
+    it('does not store history', () => {
+      const originalItemHistoryMaxLen = ItemTracked.ITEM_HISTORY_MAX_LENGTH;
+      ItemTracked.ITEM_HISTORY_MAX_LENGTH = 0;
+      const item1 = ItemTracked.ItemTracked(properties);
+
+      for (var i = 0; i < ItemTracked.ITEM_HISTORY_MAX_LENGTH + 2; i++) {
+        item1.update(properties, i);
+        expect(item1.itemHistory.length).toBe(ItemTracked.ITEM_HISTORY_MAX_LENGTH);
+      }
+
+      ItemTracked.ITEM_HISTORY_MAX_LENGTH = originalItemHistoryMaxLen;
     });
   });
 });