diff --git a/CHANGELOG.md b/CHANGELOG.md
index c255fc3..d869b26 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,17 +1,30 @@
-# Change Log
-All notable changes to this project will be documented in this file.
-
-The format is based on [Keep a Changelog](http://keepachangelog.com/)
-and this project adheres to [Semantic Versioning](http://semver.org/).
-
-## \[1.0.2\]: 2017-02-05
-### Added
--   Added `toBuffer` method for Replay class.
-
-## \[1.0.1\]: 2017-01-31
-### Changed
--   NPM package now only contains the `src\` directory.
-
-## \[1.0.0\]: 2017-01-30
-### Added
--   First package release.
+# Change Log
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+## \[1.0.3\]: 2018-10-29
+
+### Fixed
+
+- Fix critical bug with missing integrity checks making all levels invalid.
+
+## \[1.0.2\]: 2017-02-05
+
+### Added
+
+- Added `toBuffer` method for Replay class.
+
+## \[1.0.1\]: 2017-01-31
+
+### Changed
+
+- NPM package now only contains the `src\` directory.
+
+## \[1.0.0\]: 2017-01-30
+
+### Added
+
+- First package release.
diff --git a/package.json b/package.json
index 21c4dae..f0dfc8f 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "node-elma",
-  "version": "1.0.2",
+  "version": "1.0.3",
   "description": "Elasto Mania NPM package to read, modify and write Elma files",
   "main": "src/index.js",
   "scripts": {
diff --git a/src/lev.js b/src/lev.js
index 040917b..03be2a6 100644
--- a/src/lev.js
+++ b/src/lev.js
@@ -282,12 +282,52 @@ class Level {
     return output
   }
 
+  _calculateIntegrity() {
+    const pol_sum = this.polygons.reduce((accumulator, current) => {
+      return (
+        accumulator +
+        current.vertices.reduce((accumulator, current) => {
+          return accumulator + current.x + current.y;
+        }, 0)
+      );
+    }, 0);
+  
+    const obj_sum = this.objects.reduce((acc, val) => {
+      let obj_val = 0;
+      if (val.type === "exit") obj_val = 1;
+      else if (val.type === "apple") obj_val = 2;
+      else if (val.type === "killer") obj_val = 3;
+      else if (val.type === "start") obj_val = 4;
+      return acc + val.x + val.y + obj_val;
+    }, 0);
+  
+    const pic_sum = this.pictures.reduce((acc, val) => {
+      return acc + val.x + val.y;
+    }, 0);
+  
+    const sum = (pol_sum + obj_sum + pic_sum) * 3247.764325643;
+  
+    this.integrity = [
+      sum,
+      this._getRandomInt(0, 5871) + 11877 - sum,
+      this._getRandomInt(0, 5871) + 11877 - sum,
+      this._getRandomInt(0, 6102) + 12112 - sum
+    ];
+  }
+  
+  _getRandomInt(min, max) {
+    min = Math.ceil(min);
+    max = Math.floor(max);
+    return Math.floor(Math.random() * (max - min)) + min;
+  }
+
   /**
    * Internal convinience method.
    * @private
    * @returns {Promise}
    */
   _update () {
+    this._calculateIntegrity()
     return new Promise((resolve, reject) => {
       // figure out how big of a buffer to create since dynamic allocation is not a thing...
       let bufferSize = 850 // all known level attributes' size