diff --git a/bin/build.js b/bin/build.js
index 72fa92f..74ac281 100755
--- a/bin/build.js
+++ b/bin/build.js
@@ -12,4 +12,5 @@ buildProject(
   params['<src-dir>'],
   params['<build-dir>'],
   params['--lang'],
+  process.env,
 )
diff --git a/src/build.js b/src/build.js
index 3c36eb7..3a9b454 100644
--- a/src/build.js
+++ b/src/build.js
@@ -14,8 +14,8 @@ export function parseData(
   parseDataFromJsonFile,
   parseDataFromEnv,
   parseTranslations,
-  envVars = [],
   lang = null,
+  envVars = [],
 ) {
   return Promise.all([
     parseDataFromJsonFile(withSrcDir, ifPathExists, readFile, parseJson),
diff --git a/src/data.js b/src/data.js
index 39b8d49..5d18224 100644
--- a/src/data.js
+++ b/src/data.js
@@ -1,5 +1,5 @@
 const JSON_FILE_NAME = 'data.json'
-const ENV_VAR_PREFIX = '_MG_'
+const ENV_VAR_PREFIX = '__'
 
 function normalizeEnvVarName(str) {
   return (
diff --git a/src/index.js b/src/index.js
index d8f0322..d600f3c 100644
--- a/src/index.js
+++ b/src/index.js
@@ -17,6 +17,7 @@ export default async function buildProject(
   srcDirPath,
   buildDirPath,
   lang = null,
+  envVars = {},
 ) {
   await ifPathExists(buildDirPath, rmDir)
 
@@ -33,8 +34,8 @@ export default async function buildProject(
     parseDataFromJsonFile,
     parseDataFromEnv,
     parseTranslations,
-    process.env,
     lang,
+    envVars,
   )
 
   return Promise.all([
diff --git a/tests/data.test.js b/tests/data.test.js
index 2a656a9..3299d2b 100644
--- a/tests/data.test.js
+++ b/tests/data.test.js
@@ -50,9 +50,9 @@ describe('#src/data', () => {
         parseDataFromEnv({
           EDITOR: 'vim',
           LANG: 'en_US.UTF-8',
-          _MG_SECRET_PHONE_NUMBER: '+33777777777',
+          __SECRET_PHONE_NUMBER: '+33777777777',
           SHELL: '/bin/bash',
-          _MG_EMAIL_ADDRESS: 'void@null.net',
+          __EMAIL_ADDRESS: 'void@null.net',
         }),
         {
           secret_phone_number: '+33777777777',