diff --git a/index.js b/index.js
index 3ffe9f8f..bd99eb08 100644
--- a/index.js
+++ b/index.js
@@ -57,10 +57,10 @@ module.exports = {
         const include = this._getIncludes();
 
         concat(
-            this.app,
-            this._findCoveredAddon(),
-            this._findInRepoAddons()
-          )
+          this.app,
+          this._findCoveredAddon(),
+          this._findInRepoAddons()
+        )
           .filter(Boolean)
           .map(getPlugins)
           .forEach((plugins) => plugins.push([IstanbulPlugin, { exclude, include }]));
@@ -85,7 +85,7 @@ module.exports = {
     return undefined;
   },
 
-  includedCommands: function () {
+  includedCommands: function() {
     return {
       'coverage-merge': require('./lib/coverage-merge')
     };
@@ -100,7 +100,9 @@ module.exports = {
   },
 
   testemMiddleware: function(app) {
-    if (!this._isCoverageEnabled()) { return; }
+    if (!this._isCoverageEnabled()) {
+      return;
+    }
     attachMiddleware(app, {
       configPath: this.project.configPath(),
       root: this.project.root,
@@ -156,8 +158,12 @@ module.exports = {
   _getIncludesForAddonDirectory: function() {
     let addon = this._findCoveredAddon();
     if (addon) {
-      const dir = path.join(this.project.root, 'addon');
-      return this._getIncludesForDir(dir, addon.name);
+      const addonDir = path.join(this.project.root, 'addon');
+      const addonTestSupportDir = path.join(this.project.root, 'addon-test-support');
+      return concat(
+        this._getIncludesForDir(addonDir, addon.name),
+        this._getIncludesForDir(addonTestSupportDir, `${addon.name}/test-support`)
+      );
     }
   },
 
@@ -170,10 +176,12 @@ module.exports = {
       let addonDir = path.join(this.project.root, 'lib', addon.name);
       let addonAppDir = path.join(addonDir, 'app');
       let addonAddonDir = path.join(addonDir, 'addon');
+      const addonAddonTestSupportDir = path.join(addonDir, 'addon-test-support');
       return concat(
         acc,
         this._getIncludesForDir(addonAppDir, this.parent.name()),
-        this._getIncludesForDir(addonAddonDir, addon.name)
+        this._getIncludesForDir(addonAddonDir, addon.name),
+        this._getIncludesForDir(addonAddonTestSupportDir, `${addon.name}/test-support`)
       );
     }, []);
   },
@@ -185,14 +193,18 @@ module.exports = {
    * @returns {Array<String>} include paths
    */
   _getIncludesForDir: function(dir, prefix) {
-    let dirname = path.relative(this.project.root, dir);
-    let globs = this.registry.extensionsForType('js').map((extension) => `**/*.${extension}`);
-
-    return walkSync(dir, { directories: false, globs }).map(file => {
-      let module = prefix + '/' + file.replace(EXT_RE, '.js');
-      this.fileLookup[module] = path.join(dirname, file);
-      return module;
-    });
+    if (fs.existsSync(dir)) {
+      let dirname = path.relative(this.project.root, dir);
+      let globs = this.registry.extensionsForType('js').map((extension) => `**/*.${extension}`);
+
+      return walkSync(dir, { directories: false, globs }).map(file => {
+        let module = prefix + '/' + file.replace(EXT_RE, '.js');
+        this.fileLookup[module] = path.join(dirname, file);
+        return module;
+      });
+    } else {
+      return [];
+    }
   },
 
   /**
diff --git a/test/fixtures/my-addon/addon-test-support/uncovered-test-support.js b/test/fixtures/my-addon/addon-test-support/uncovered-test-support.js
new file mode 100644
index 00000000..21a3f3f7
--- /dev/null
+++ b/test/fixtures/my-addon/addon-test-support/uncovered-test-support.js
@@ -0,0 +1,14 @@
+/**
+ * Just a test function to show that addon-test-support coverage is counted
+ */
+export function uncoveredFunction(condition) {
+  if (condition) {
+    return 'Was true';
+  } else {
+    return 'Was false';
+  }
+}
+
+export function anotherUncoveredFunction() {
+  return 'Not covered';
+}
diff --git a/test/fixtures/my-app-with-in-repo-addon/lib/my-in-repo-addon/addon-test-support/uncovered-test-support.js b/test/fixtures/my-app-with-in-repo-addon/lib/my-in-repo-addon/addon-test-support/uncovered-test-support.js
new file mode 100644
index 00000000..21a3f3f7
--- /dev/null
+++ b/test/fixtures/my-app-with-in-repo-addon/lib/my-in-repo-addon/addon-test-support/uncovered-test-support.js
@@ -0,0 +1,14 @@
+/**
+ * Just a test function to show that addon-test-support coverage is counted
+ */
+export function uncoveredFunction(condition) {
+  if (condition) {
+    return 'Was true';
+  } else {
+    return 'Was false';
+  }
+}
+
+export function anotherUncoveredFunction() {
+  return 'Not covered';
+}
diff --git a/test/integration/in-repo-addon-coverage-test.js b/test/integration/in-repo-addon-coverage-test.js
index 90e15cd4..eac01d5f 100644
--- a/test/integration/in-repo-addon-coverage-test.js
+++ b/test/integration/in-repo-addon-coverage-test.js
@@ -58,10 +58,22 @@ describe('in-repo addon coverage generation', function() {
     return app.run('ember', 'test').then(function() {
       expect(file(`${app.path}/coverage/lcov-report/index.html`)).to.not.be.empty;
       expect(file(`${app.path}/coverage/index.html`)).to.not.be.empty;
-      var summary = fs.readJSONSync(`${app.path}/coverage/coverage-summary.json`);
-      expect(summary.total.lines.pct).to.equal(75);
+
+      const summary = fs.readJSONSync(`${app.path}/coverage/coverage-summary.json`);
+      expect(summary.total.lines.pct).to.equal(50);
       expect(summary['app/utils/my-covered-util-app.js'].lines.total).to.equal(1);
+
+      // Check that lib/my-in-repo-addon/utils/my-covered-utill is 1 line and that 1 line is covered
       expect(summary['lib/my-in-repo-addon/addon/utils/my-covered-util.js'].lines.total).to.equal(1);
+      expect(summary['lib/my-in-repo-addon/addon/utils/my-covered-util.js'].lines.covered).to.equal(1);
+
+      // Check that lib/my-in-repo-addon/utils/my-uncovered-utill is 1 line and that 0 lines are covered
+      expect(summary['lib/my-in-repo-addon/addon/utils/my-uncovered-util.js'].lines.total).to.equal(1);
+      expect(summary['lib/my-in-repo-addon/addon/utils/my-uncovered-util.js'].lines.covered).to.equal(0);
+
+      // Check that lib/my-in-repo-addon/addon-test-support/uncovered-test-support is 4 lines and that 0 lines are covered
+      expect(summary['lib/my-in-repo-addon/addon-test-support/uncovered-test-support.js'].lines.total).to.equal(4);
+      expect(summary['lib/my-in-repo-addon/addon-test-support/uncovered-test-support.js'].lines.covered).to.equal(0);
     });
   }));
 });
diff --git a/test/unit/index-test.js b/test/unit/index-test.js
index e6a3ca43..3266fe62 100644
--- a/test/unit/index-test.js
+++ b/test/unit/index-test.js
@@ -419,9 +419,11 @@ describe('index.js', function() {
           const includes = Index._getIncludesForAddonDirectory();
           expect(includes).to.deep.equal([
             'my-addon/utils/my-covered-util.js',
-            'my-addon/utils/my-uncovered-util.js'
+            'my-addon/utils/my-uncovered-util.js',
+            'my-addon/test-support/uncovered-test-support.js'
           ]);
           expect(Index.fileLookup).to.deep.equal({
+            'my-addon/test-support/uncovered-test-support.js': 'addon-test-support/uncovered-test-support.js',
             'my-addon/utils/my-covered-util.js': 'addon/utils/my-covered-util.js',
             'my-addon/utils/my-uncovered-util.js': 'addon/utils/my-uncovered-util.js'
           });
@@ -473,13 +475,15 @@ describe('index.js', function() {
             'my-app/utils/my-covered-util.js',
             'my-app/utils/my-uncovered-util.js',
             'my-in-repo-addon/utils/my-covered-util.js',
-            'my-in-repo-addon/utils/my-uncovered-util.js'
+            'my-in-repo-addon/utils/my-uncovered-util.js',
+            'my-in-repo-addon/test-support/uncovered-test-support.js'
           ]);
           expect(Index.fileLookup).to.deep.equal({
             'my-app/utils/my-covered-util.js': 'lib/my-in-repo-addon/app/utils/my-covered-util.js',
             'my-app/utils/my-uncovered-util.js': 'lib/my-in-repo-addon/app/utils/my-uncovered-util.js',
             'my-in-repo-addon/utils/my-covered-util.js': 'lib/my-in-repo-addon/addon/utils/my-covered-util.js',
             'my-in-repo-addon/utils/my-uncovered-util.js': 'lib/my-in-repo-addon/addon/utils/my-uncovered-util.js',
+            'my-in-repo-addon/test-support/uncovered-test-support.js': 'lib/my-in-repo-addon/addon-test-support/uncovered-test-support.js'
           });
         });
       });