diff --git a/lib/main.js b/lib/main.js
index eb96e7fd..5da0ea71 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -60,7 +60,9 @@ function config (options) {
     var parsedObj = parse(fs.readFileSync(path, { encoding: encoding }))
 
     Object.keys(parsedObj).forEach(function (key) {
-      process.env[key] = process.env[key] || parsedObj[key]
+      if (!process.env.hasOwnProperty(key)) {
+        process.env[key] = parsedObj[key]
+      }
     })
 
     return { parsed: parsedObj }
diff --git a/test/main.js b/test/main.js
index 7d6c3cf1..f373ed50 100644
--- a/test/main.js
+++ b/test/main.js
@@ -74,6 +74,15 @@ describe('dotenv', function () {
       done()
     })
 
+    it('does not write over keys already in process.env if the key has a falsy value', function (done) {
+      process.env.test = ''
+      // 'val' returned as value in `beforeEach`. should keep this ''
+      dotenv.config()
+
+      process.env.test.should.eql('')
+      done()
+    })
+
     it('returns parsed object', function (done) {
       var env = dotenv.config()