diff --git a/lib/index.js b/lib/index.js
index dcbc161..e6fb181 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -4,8 +4,8 @@ const Filter = require('broccoli-persistent-filter');
 const CLIEngine = require('eslint').CLIEngine;
 const md5Hex = require('md5-hex');
 const stringify = require('json-stable-stringify');
-const sep = require('path').sep;
-const BUILD_DIR_REGEX = new RegExp('(' + sep + ')?build(' + sep + ')?$');
+const path = require('path');
+const BUILD_DIR_REGEX = new RegExp('(' + path.sep + ')?build(' + path.sep + ')?$');
 
 
 /**
@@ -108,19 +108,24 @@ EslintValidationFilter.prototype.baseDir = function baseDir() {
 };
 
 EslintValidationFilter.prototype.cacheKeyProcessString = function cacheKeyProcessString(content, relativePath) {
-  return md5Hex([content, relativePath, stringify(this.options, {
-    replacer(key, value) {
-      if (typeof value === 'function') {
-        return value.toString();
-      }
-      return value;
+  function functionStringifier(key, value) {
+    if (typeof value === 'function') {
+      return value.toString();
     }
-  })]);
+    return value;
+  }
+
+  return md5Hex([
+    content,
+    relativePath,
+    stringify(this.options, {replacer: functionStringifier}),
+    stringify(this.cli.getConfigForFile(path.join(this.eslintrc, relativePath)))
+  ]);
 };
 
 EslintValidationFilter.prototype.processString = function processString(content, relativePath) {
   // verify file content
-  const output = this.cli.executeOnText(content, this.eslintrc + '/' + relativePath);
+  const output = this.cli.executeOnText(content, path.join(this.eslintrc, relativePath));
   const filteredOutput = filterAllIgnoredFileMessages(output);
   const toCache = {
     lint: filteredOutput,
diff --git a/test/test.js b/test/test.js
index b1a57b9..744fca8 100644
--- a/test/test.js
+++ b/test/test.js
@@ -1,4 +1,5 @@
 const fs = require('fs');
+const path = require('path');
 const expect = require('chai').expect;
 const eslint = require('../index');
 const runEslint = require('./helpers/run-eslint');
@@ -10,6 +11,19 @@ const DOUBLEQUOTE = 'Strings must use doublequote.';
 const FILEPATH = 'fixture/1.js';
 
 describe('EslintValidationFilter', function describeEslintValidationFilter() {
+  before(function beforeEslintValidationFilter() {
+    this.setupSpies = function setupSpies() {
+      // spy on filter process methods
+      const processStringSpy = this.sinon.spy(eslint.prototype, 'processString');
+      const postProcessSpy = this.sinon.spy(eslint.prototype, 'postProcess');
+
+      return {
+        processStringSpy,
+        postProcessSpy
+      };
+    };
+  });
+
   function shouldReportErrors() {
     // lint test fixtures
     const promise = runEslint(FIXTURES);
@@ -67,9 +81,10 @@ describe('EslintValidationFilter', function describeEslintValidationFilter() {
   });
 
   it('should cache results, but still log errors', function shouldHaveCachedResults() {
-    // spy on filter process methods
-    const processStringSpy = this.sinon.spy(eslint.prototype, 'processString');
-    const postProcessSpy = this.sinon.spy(eslint.prototype, 'postProcess');
+    const {
+      processStringSpy,
+      postProcessSpy
+    } = this.setupSpies();
 
     // run first test again, should use cache but still log errors
     return shouldReportErrors()
@@ -81,9 +96,10 @@ describe('EslintValidationFilter', function describeEslintValidationFilter() {
   });
 
   it('should allow disabling the cache', function shouldAllowDisablingCache() {
-    // spy on filter process methods
-    const processStringSpy = this.sinon.spy(eslint.prototype, 'processString');
-    const postProcessSpy = this.sinon.spy(eslint.prototype, 'postProcess');
+    const {
+      processStringSpy,
+      postProcessSpy
+    } = this.setupSpies();
 
     function runNonpersistent() {
       return runEslint(FIXTURES, {
@@ -100,4 +116,50 @@ describe('EslintValidationFilter', function describeEslintValidationFilter() {
       expect(postProcessSpy, 'Logged errors (twice)').to.have.callCount(6);
     });
   });
+
+  it('should use the configuration to cache results', function shouldCacheByConfig() {
+    const {
+      processStringSpy,
+      postProcessSpy
+    } = this.setupSpies();
+    let processStringInitialCount;
+    let postProcessInitialCount;
+    const eslintrcPath = path.join(FIXTURES, '.eslintrc');
+    let eslintrcContent;
+
+    function runCustomRule() {
+      return runEslint(FIXTURES, {
+        options: {
+          rulePaths: ['conf/rules']
+        }
+      });
+    }
+
+    return runCustomRule().then(function retrieveCallCount() {
+      processStringInitialCount = processStringSpy.callCount;
+      postProcessInitialCount = postProcessSpy.callCount;
+    })
+    .then(function backupConfig() {
+      eslintrcContent = fs.readFileSync(eslintrcPath);
+    })
+    .then(function writeNewConfig() {
+      fs.writeFileSync(eslintrcPath, JSON.stringify({
+        extends: 'nightmare-mode/node',
+        rules: {
+          'custom-no-alert': 2
+        }
+      }));
+    })
+    .then(runCustomRule)
+    .then(function assertCaching() {
+      // check that it did not use the cache
+      expect(processStringSpy, 'Didn\'t use cache').to.have.callCount(processStringInitialCount + 3);
+      expect(postProcessSpy, 'Logged errors').to.have.callCount(postProcessInitialCount + 3);
+    })
+    .finally(function restoreConfig() {
+      if (typeof eslintrcContent !== 'undefined') {
+        fs.writeFileSync(eslintrcPath, eslintrcContent);
+      }
+    });
+  });
 });