diff --git a/package-lock.json b/package-lock.json
index c429ca4..727fe8d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -34,6 +34,12 @@
         "sprintf-js": "~1.0.2"
       }
     },
+    "assertion-error": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/assertion-error/-/assertion-error-1.1.0.tgz",
+      "integrity": "sha512-jgsaNduz+ndvGyFt3uSuWqvy4lCnIJiovtouQN5JZHOKCS2QuhEdbcQHFhVksz2N2U9hXJo8odG7ETyWlEeuDw==",
+      "dev": true
+    },
     "babel-code-frame": {
       "version": "6.26.0",
       "resolved": "https://registry.npmjs.org/babel-code-frame/-/babel-code-frame-6.26.0.tgz",
@@ -130,10 +136,18 @@
       "dev": true
     },
     "chai": {
-      "version": "1.4.2",
-      "resolved": "https://registry.npmjs.org/chai/-/chai-1.4.2.tgz",
-      "integrity": "sha1-i/jpPjaQFxzyYy56ETUUvDs7B2o=",
-      "dev": true
+      "version": "4.2.0",
+      "resolved": "https://registry.npmjs.org/chai/-/chai-4.2.0.tgz",
+      "integrity": "sha512-XQU3bhBukrOsQCuwZndwGcCVQHyZi53fQ6Ys1Fym7E4olpIqqZZhhoFJoaKVvV17lWQoXYwgWN2nF5crA8J2jw==",
+      "dev": true,
+      "requires": {
+        "assertion-error": "^1.1.0",
+        "check-error": "^1.0.2",
+        "deep-eql": "^3.0.1",
+        "get-func-name": "^2.0.0",
+        "pathval": "^1.1.0",
+        "type-detect": "^4.0.5"
+      }
     },
     "chalk": {
       "version": "1.1.3",
@@ -154,6 +168,12 @@
         }
       }
     },
+    "check-error": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/check-error/-/check-error-1.0.2.tgz",
+      "integrity": "sha1-V00xLt2Iu13YkS6Sht1sCu1KrII=",
+      "dev": true
+    },
     "cli": {
       "version": "0.4.5",
       "resolved": "https://registry.npmjs.org/cli/-/cli-0.4.5.tgz",
@@ -275,6 +295,15 @@
       "integrity": "sha1-9lNNFRSCabIDUue+4m9QH5oZEpA=",
       "dev": true
     },
+    "deep-eql": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/deep-eql/-/deep-eql-3.0.1.tgz",
+      "integrity": "sha512-+QeIQyN5ZuO+3Uk5DYh6/1eKO0m0YmJFGNmFHGACpf1ClL1nmlV/p4gNgbl2pJGxgXb4faqo6UE+M5ACEMyVcw==",
+      "dev": true,
+      "requires": {
+        "type-detect": "^4.0.0"
+      }
+    },
     "define-properties": {
       "version": "1.1.3",
       "resolved": "https://registry.npmjs.org/define-properties/-/define-properties-1.1.3.tgz",
@@ -443,6 +472,12 @@
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       "dev": true
     },
+    "get-func-name": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/get-func-name/-/get-func-name-2.0.0.tgz",
+      "integrity": "sha1-6td0q+5y4gQJQzoGY2YCPdaIekE=",
+      "dev": true
+    },
     "get-stream": {
       "version": "4.1.0",
       "resolved": "https://registry.npmjs.org/get-stream/-/get-stream-4.1.0.tgz",
@@ -1063,6 +1098,12 @@
       "resolved": "https://registry.npmjs.org/path-parse/-/path-parse-1.0.6.tgz",
       "integrity": "sha512-GSmOT2EbHrINBf9SR7CDELwlJ8AENk3Qn7OikK4nFYAu3Ote2+JYNVvkpAEQm3/TLNEJFD/xZJjzyxg3KBWOzw=="
     },
+    "pathval": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/pathval/-/pathval-1.1.0.tgz",
+      "integrity": "sha1-uULm1L3mUwBe9rcTYd74cn0GReA=",
+      "dev": true
+    },
     "protochain": {
       "version": "1.0.5",
       "resolved": "https://registry.npmjs.org/protochain/-/protochain-1.0.5.tgz",
@@ -1340,6 +1381,12 @@
       "resolved": "https://registry.npmjs.org/to-fast-properties/-/to-fast-properties-1.0.3.tgz",
       "integrity": "sha1-uDVx+k2MJbguIxsG46MFXeTKGkc="
     },
+    "type-detect": {
+      "version": "4.0.8",
+      "resolved": "https://registry.npmjs.org/type-detect/-/type-detect-4.0.8.tgz",
+      "integrity": "sha512-0fr/mIH1dlO+x7TlcMy+bIDqKPsw/70tVyeHW787goQjhmqaZe10uwLujubK9q9Lg6Fiho1KUKDYz0Z7k7g5/g==",
+      "dev": true
+    },
     "underscore": {
       "version": "1.4.4",
       "resolved": "https://registry.npmjs.org/underscore/-/underscore-1.4.4.tgz",
diff --git a/package.json b/package.json
index 7edf63b..9e942ad 100644
--- a/package.json
+++ b/package.json
@@ -42,7 +42,7 @@
     "url": "http://blog.millermedeiros.com/"
   },
   "devDependencies": {
-    "chai": "1.4",
+    "chai": "^4.2.0",
     "esformatter-pipe-test": "file:test/pipe",
     "esformatter-preset-fake-1": "file:test/preset/fake1",
     "esformatter-preset-fake-2": "file:test/preset/fake2",