diff --git a/.prettierignore b/.prettierignore
index d9ff83d..a3dd4f8 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -1,5 +1,5 @@
 node_modules
 dist
-
+coverage
 package.json
 package-lock.json
diff --git a/.travis.yml b/.travis.yml
index b37b152..c1a3d85 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -12,7 +12,7 @@ node_js:
 sudo: false
 
 before_install:
-  - curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version 0.27.5
+  - curl -o- -L https://yarnpkg.com/install.sh | bash -s -- --version 1.3.2
   - export PATH=$HOME/.yarn/bin:$PATH
 
 cache:
diff --git a/lib/format-results.js b/lib/format-results.js
index 1c295a0..af220d5 100644
--- a/lib/format-results.js
+++ b/lib/format-results.js
@@ -32,7 +32,8 @@ const constructSummary = rules =>
     .map((rule, i) => {
       const errors = pad(rule.errors, maxErrorLen(rules));
       const warnings = pad(rule.warnings, maxWarningLen(rules));
-      const line = chalk`errors {red ${errors}} warnings {yellow ${warnings}} rule: {gray ${rule.ruleId}}`;
+      const { ruleId } = rule;
+      const line = chalk`errors {red ${errors}} warnings {yellow ${warnings}} rule: {gray ${ruleId}}`;
       return i < rules.length - 1 ? `${line}\n` : line;
     })
     .join('');
diff --git a/package.json b/package.json
index b8e0c4a..38b5e6c 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "eslint-formatter-summary",
-  "version": "1.0.1",
+  "version": "1.0.2",
   "description": "ESLint summary formatter aggregating results by rule",
   "main": "index.js",
   "author": "Marton Hipszki <mhipszki@gmail.com>",
@@ -76,6 +76,6 @@
     "coveralls": "^3.0.0",
     "eslint": "^4.3.0",
     "jest": "^21.2.1",
-    "prettier": "1.7.4"
+    "prettier": "1.9.0"
   }
 }
diff --git a/yarn.lock b/yarn.lock
index 58ae3d3..16b2277 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -2658,9 +2658,9 @@ preserve@^0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/preserve/-/preserve-0.2.0.tgz#815ed1f6ebc65926f865b310c0713bcb3315ce4b"
 
-prettier@1.7.4:
-  version "1.7.4"
-  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.7.4.tgz#5e8624ae9363c80f95ec644584ecdf55d74f93fa"
+prettier@1.9.0:
+  version "1.9.0"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.9.0.tgz#1a7205bdb6126b30cf8c0a7b2b86997162e1ee3e"
 
 pretty-format@^21.2.1:
   version "21.2.1"
@@ -3394,7 +3394,30 @@ yargs-parser@^7.0.0:
   dependencies:
     camelcase "^4.1.0"
 
-yargs@^9.0.0, yargs@^9.0.1:
+yargs-parser@^8.0.0:
+  version "8.0.0"
+  resolved "https://registry.yarnpkg.com/yargs-parser/-/yargs-parser-8.0.0.tgz#21d476330e5a82279a4b881345bf066102e219c6"
+  dependencies:
+    camelcase "^4.1.0"
+
+yargs@^10.0.3:
+  version "10.0.3"
+  resolved "https://registry.yarnpkg.com/yargs/-/yargs-10.0.3.tgz#6542debd9080ad517ec5048fb454efe9e4d4aaae"
+  dependencies:
+    cliui "^3.2.0"
+    decamelize "^1.1.1"
+    find-up "^2.1.0"
+    get-caller-file "^1.0.1"
+    os-locale "^2.0.0"
+    require-directory "^2.1.1"
+    require-main-filename "^1.0.1"
+    set-blocking "^2.0.0"
+    string-width "^2.0.0"
+    which-module "^2.0.0"
+    y18n "^3.2.1"
+    yargs-parser "^8.0.0"
+
+yargs@^9.0.0:
   version "9.0.1"
   resolved "https://registry.yarnpkg.com/yargs/-/yargs-9.0.1.tgz#52acc23feecac34042078ee78c0c007f5085db4c"
   dependencies: