diff --git a/README.md b/README.md
index 2e4b9ae..b8935f4 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
   <h1>💋 FrenchKiss.js</h1>
 
 [![Build Status](https://travis-ci.com/koala-interactive/frenchkiss.js.svg?branch=master)](https://travis-ci.com/koala-interactive/frenchkiss.js)
-[![File size](https://img.shields.io/badge/GZIP%20size-1028%20B-brightgreen.svg)](./dist/umd/frenchkiss.js)
+[![File size](https://img.shields.io/badge/GZIP%20size-1087%20B-brightgreen.svg)](./dist/umd/frenchkiss.js)
 ![](https://img.shields.io/badge/dependencies-none-brightgreen.svg)
 ![](https://img.shields.io/snyk/vulnerabilities/github/koala-interactive/frenchkiss.js.svg)
 [![License: MIT](https://img.shields.io/badge/License-MIT-brightgreen.svg)](https://opensource.org/licenses/MIT)
@@ -57,6 +57,7 @@ Or install using [npm](https://npmjs.org):
 - [frenchkiss.unset()](#frenchkiss.unsetlanguage-string)
 - [frenchkiss.fallback()](#frenchkissfallbacklanguage-string-string)
 - [frenchkiss.onMissingKey()](#frenchkissonMissingKeyfn-Function)
+- [frenchkiss.onMissingVariable()](#frenchkissonMissingVariablefn-Function)
 - [SELECT expression](#select-expression)
 - [PLURAL expression](#plural-expression)
 - [Plural category](#plural-category)
@@ -215,6 +216,31 @@ frenchkiss.t('missingkey'); // => 'An error happened (missingkey)'
 
 ---
 
+### frenchkiss.onMissingVariable(fn: Function)
+
+It's possible to handle missing variables, sending errors to your monitoring server or handle it directly by returning something to replace with.
+
+```js
+frenchkiss.set('en', {
+  hello: 'Hello {name} !',
+});
+frenchkiss.locale('en');
+
+frenchkiss.t('hello'); // => 'Hello  !'
+
+frenchkiss.onMissingVariable((variable, key, language) => {
+  // Send error to your server
+  sendReport(`Missing the variable "${variable}" in ${language}->${key}.`);
+
+  // Returns the text you want
+  return `[missing:${variable}]`;
+});
+
+frenchkiss.t('hello'); // => 'Hello [missing:name] !'
+```
+
+---
+
 ### SELECT expression
 
 If you need to display different text messages depending on the value of a variable, you need to translate all of those text messages... or you can handle this with a select ICU expression.
diff --git a/package.json b/package.json
index e86c982..040ae33 100644
--- a/package.json
+++ b/package.json
@@ -43,6 +43,7 @@
     "@babel/preset-env": "^7.1.6",
     "@babel/register": "^7.0.0",
     "chai": "^4.2.0",
+    "chai-spies": "^1.0.0",
     "del-cli": "^1.1.0",
     "eslint": "^5.12.1",
     "eslint-config-prettier": "^4.0.0",
diff --git a/src/compiler.js b/src/compiler.js
index 1226789..25cf739 100644
--- a/src/compiler.js
+++ b/src/compiler.js
@@ -19,13 +19,22 @@ const escapeText = JSON.stringify; // (text) => '"' + text.replace(/(["\\])/g, '
 
 /**
  * Helper to bind variable name to value.
- * Default to empty string if not defined
+ * Default to onMissingVariable returns if not defined
+ *
+ * Mapping :
+ * - undefined -> ''
+ * - null -> ''
+ * - 0 -> 0
+ * - 155 -> 155
+ * - 'test' -> 'test'
+ * - not defined -> onMissingVariable(value, key, language)
  *
  * @param {String} text
  * @returns {String}
  */
 const escapeVariable = text =>
-  '(p["' + text + '"]||(p["' + text + '"]=="0"?0:""))';
+  // prettier-ignore
+  '(p["' + text + '"]||(p["' + text + '"]=="0"?0:"' + text + '" in p?"":v("' + text + '",k,l)))';
 
 /**
  * Compile the translation to executable optimized function
@@ -48,8 +57,11 @@ export function compileCode(text) {
   }
 
   return new Function(
-    'a',
-    'f',
+    'a', // params
+    'f', // plural category function
+    'k', // key
+    'l', // language
+    'v', // missingVariableHandler
     'var p=a||{}' +
       (size ? ',m=f?{' + pluralCode + '}:{}' : '') +
       ';return ' +
diff --git a/src/frenchkiss.js b/src/frenchkiss.js
index 8521816..671bafd 100644
--- a/src/frenchkiss.js
+++ b/src/frenchkiss.js
@@ -18,6 +18,17 @@ let _fallback = '';
  */
 let missingKeyHandler = key => key;
 
+/**
+ * Default function used in case of missing variable
+ * Returns the value you want
+ *
+ * @param {String} variable
+ * @param {String} key
+ * @param {String} language
+ * @returns {String}
+ */
+let missingVariableHandler = () => '';
+
 /**
  * Get back a translation and returns the optimized function
  * Store the function in the cache to re-use it
@@ -54,17 +65,27 @@ export const t = (key, params, language) => {
   let fn,
     lang = language || _locale;
 
+  // Try to get the specified or locale
   if (lang) {
     fn = getCompiledCode(key, lang);
+
+    if (fn) {
+      return fn(params, _plural[lang], key, lang, missingVariableHandler);
+    }
   }
 
+  lang = _fallback;
+
   // Try to get the fallback language
-  if (!fn && _fallback) {
-    lang = _fallback;
+  if (lang) {
     fn = getCompiledCode(key, lang);
+
+    if (fn) {
+      return fn(params, _plural[lang], key, lang, missingVariableHandler);
+    }
   }
 
-  return fn ? fn(params, _plural[lang]) : missingKeyHandler(key);
+  return missingKeyHandler(key);
 };
 
 /**
@@ -78,6 +99,17 @@ export const onMissingKey = fn => {
   missingKeyHandler = fn;
 };
 
+/**
+ * Set a function to handle missing variable to:
+ * - Returns the value you want
+ * - Report the poblem to your server
+ *
+ * @param {Function} fn
+ */
+export const onMissingVariable = fn => {
+  missingVariableHandler = fn;
+};
+
 /**
  * Getter/setter for locale
  *
@@ -171,6 +203,7 @@ export default {
   store,
   t,
   onMissingKey,
+  onMissingVariable,
   locale,
   fallback,
   set,
diff --git a/test/index.js b/test/index.js
index 657541b..2a13e97 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,6 +1,9 @@
-import { expect } from 'chai';
+import chai, { expect } from 'chai';
+import spies from 'chai-spies';
 import i18n from '../src/frenchkiss';
 
+chai.use(spies);
+
 describe('locale', () => {
   it('should not bug if no locale', () => {
     expect(i18n.t('test')).to.equal('test');
@@ -237,6 +240,7 @@ describe('t', () => {
 describe('onMissingKey', () => {
   beforeEach(() => {
     i18n.locale('en');
+    i18n.fallback('xyz');
   });
 
   afterEach(() => {
@@ -247,6 +251,15 @@ describe('onMissingKey', () => {
     expect(i18n.t('bogus_key')).to.equal('bogus_key');
   });
 
+  it('is called with key', () => {
+    const fn = chai.spy(() => '');
+
+    i18n.onMissingKey(fn);
+    i18n.t('bogus_key');
+
+    expect(fn).to.have.been.called.with('bogus_key');
+  });
+
   it('replace the key with something custom when not found', () => {
     i18n.onMissingKey(key => 'missing:' + key);
     expect(i18n.t('bogus_key')).to.equal('missing:bogus_key');
@@ -261,6 +274,42 @@ describe('onMissingKey', () => {
   });
 });
 
+describe('onMissingVariable', () => {
+  beforeEach(() => {
+    i18n.locale('en');
+    i18n.set('en', {
+      test: 'Test {value} !',
+    });
+  });
+
+  afterEach(() => {
+    i18n.onMissingVariable(() => '');
+  });
+
+  it('returns empty string if variable not found', () => {
+    expect(i18n.t('test')).to.equal('Test  !');
+  });
+
+  it('returns empty string if variable not found', () => {
+    i18n.onMissingVariable(value => `[${value}]`);
+    expect(i18n.t('test', { value: '' })).to.equal('Test  !');
+  });
+
+  it('call onMissingVariable with parameters', () => {
+    const fn = chai.spy(() => '');
+
+    i18n.onMissingVariable(fn);
+    i18n.t('test');
+
+    expect(fn).to.have.been.called.with('value', 'test', 'en');
+  });
+
+  it('replace the variable with something custom when not found', () => {
+    i18n.onMissingVariable(value => `[${value}]`);
+    expect(i18n.t('test')).to.equal('Test [value] !');
+  });
+});
+
 describe('set', () => {
   beforeEach(() => {
     i18n.locale('en');