diff --git a/.travis.yml b/.travis.yml
index 5737015..d669492 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,4 @@
 language: node_js
 node_js:
-  - "0.12"
-  - "0.10"
-  - "iojs"
+  - 4
+  - 6
diff --git a/package.json b/package.json
index c3e7e90..01f795d 100644
--- a/package.json
+++ b/package.json
@@ -1,26 +1,26 @@
 {
   "name": "css-modules-loader-core",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "description": "A loader-agnostic CSS Modules implementation, based on PostCSS",
   "main": "lib/index.js",
   "directories": {
     "test": "test"
   },
   "dependencies": {
-    "icss-replace-symbols": "1.0.2",
-    "postcss": "5.0.10",
-    "postcss-modules-values": "1.1.2",
-    "postcss-modules-extract-imports": "1.0.0",
-    "postcss-modules-local-by-default": "1.0.1",
-    "postcss-modules-scope": "1.0.0"
+    "icss-replace-symbols": "1.1.0",
+    "postcss": "6.0.1",
+    "postcss-modules-extract-imports": "1.1.0",
+    "postcss-modules-local-by-default": "1.2.0",
+    "postcss-modules-scope": "1.1.0",
+    "postcss-modules-values": "1.3.0"
   },
   "devDependencies": {
     "babel": "5.8.29",
-    "babel-eslint": "4.1.3",
-    "babelify": "6.4.0",
+    "babel-eslint": "7.1.0",
+    "babelify": "7.3.0",
     "chokidar-cli": "1.1.0",
-    "eslint": "1.7.2",
-    "mocha": "2.3.3"
+    "eslint": "3.10.1",
+    "mocha": "3.1.2"
   },
   "scripts": {
     "lint": "eslint src",
diff --git a/src/file-system-loader.js b/src/file-system-loader.js
index 2a3f47d..e26c2c0 100644
--- a/src/file-system-loader.js
+++ b/src/file-system-loader.js
@@ -23,6 +23,7 @@ export default class FileSystemLoader {
   constructor( root, plugins ) {
     this.root = root
     this.sources = {}
+    this.traces = {}
     this.importNr = 0
     this.core = new Core(plugins)
     this.tokensByFile = {};
@@ -51,7 +52,8 @@ export default class FileSystemLoader {
         if ( err ) reject( err )
         this.core.load( source, rootRelativePath, trace, this.fetch.bind( this ) )
           .then( ( { injectableSource, exportTokens } ) => {
-            this.sources[trace] = injectableSource
+            this.sources[fileRelativePath] = injectableSource
+            this.traces[trace] = fileRelativePath
             this.tokensByFile[fileRelativePath] = exportTokens
             resolve( exportTokens )
           }, reject )
@@ -60,7 +62,16 @@ export default class FileSystemLoader {
   }
 
   get finalSource() {
-    return Object.keys( this.sources ).sort( traceKeySorter ).map( s => this.sources[s] )
-      .join( "" )
+    const traces = this.traces
+    const sources = this.sources
+    let written = new Set()
+
+    return Object.keys( traces ).sort( traceKeySorter ).map(key => {
+      const filename = traces[key]
+      if (written.has(filename)) { return null }
+      written.add(filename)
+
+      return sources[filename];
+    }).join( "" )
   }
 }
diff --git a/test/test-cases/values/source.css b/test/test-cases/values/source.css
index 2c63c32..3953a8d 100644
--- a/test/test-cases/values/source.css
+++ b/test/test-cases/values/source.css
@@ -1,4 +1,5 @@
-@value borders: "./borders.css", breakpoints: "./breakpoints.css";
+@value borders: "./borders.css";
+@value breakpoints: "./breakpoints.css";
 @value small, medium from breakpoints;
 @value secondary, primary as blue from "./colors.css";