diff --git a/package.json b/package.json
index 1110d96..00513f6 100644
--- a/package.json
+++ b/package.json
@@ -37,7 +37,7 @@
     "babel-preset-es2015": "^6.3.13",
     "babel-preset-stage-2": "^6.3.13",
     "benchmark": "^1.0.0",
-    "chai": "^3.2.0",
+    "chai": "^4.2.0",
     "eslint": "^4.19.1",
     "eslint-config-airbnb-base": "^11.1.3",
     "eslint-config-prettier": "^4.0.0",
diff --git a/yarn.lock b/yarn.lock
index c0f1029..05701e9 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -267,7 +267,7 @@ assert@^1.1.1:
   dependencies:
     util "0.10.3"
 
-assertion-error@^1.0.1:
+assertion-error@^1.1.0:
   version "1.1.0"
   resolved "https://registry.yarnpkg.com/assertion-error/-/assertion-error-1.1.0.tgz#e60b6b0e8f301bd97e5375215bda406c85118c0b"
   integrity sha512-jgsaNduz+ndvGyFt3uSuWqvy4lCnIJiovtouQN5JZHOKCS2QuhEdbcQHFhVksz2N2U9hXJo8odG7ETyWlEeuDw==
@@ -1213,14 +1213,17 @@ center-align@^0.1.1:
     align-text "^0.1.3"
     lazy-cache "^1.0.3"
 
-chai@^3.2.0:
-  version "3.5.0"
-  resolved "https://registry.yarnpkg.com/chai/-/chai-3.5.0.tgz#4d02637b067fe958bdbfdd3a40ec56fef7373247"
-  integrity sha1-TQJjewZ/6Vi9v906QOxW/vc3Mkc=
+chai@^4.2.0:
+  version "4.2.0"
+  resolved "https://registry.yarnpkg.com/chai/-/chai-4.2.0.tgz#760aa72cf20e3795e84b12877ce0e83737aa29e5"
+  integrity sha512-XQU3bhBukrOsQCuwZndwGcCVQHyZi53fQ6Ys1Fym7E4olpIqqZZhhoFJoaKVvV17lWQoXYwgWN2nF5crA8J2jw==
   dependencies:
-    assertion-error "^1.0.1"
-    deep-eql "^0.1.3"
-    type-detect "^1.0.0"
+    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@^1.0.0, chalk@^1.1.1, chalk@^1.1.3:
   version "1.1.3"
@@ -1247,6 +1250,11 @@ chardet@^0.4.0:
   resolved "https://registry.yarnpkg.com/chardet/-/chardet-0.4.2.tgz#b5473b33dc97c424e5d98dc87d55d4d8a29c8bf2"
   integrity sha1-tUc7M9yXxCTl2Y3IfVXU2KKci/I=
 
+check-error@^1.0.2:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/check-error/-/check-error-1.0.2.tgz#574d312edd88bb5dd8912e9286dd6c0aed4aac82"
+  integrity sha1-V00xLt2Iu13YkS6Sht1sCu1KrII=
+
 chokidar@^1.0.0, chokidar@^1.4.1:
   version "1.7.0"
   resolved "https://registry.yarnpkg.com/chokidar/-/chokidar-1.7.0.tgz#798e689778151c8076b4b360e5edd28cda2bb468"
@@ -1615,12 +1623,12 @@ decode-uri-component@^0.2.0:
   resolved "https://registry.yarnpkg.com/decode-uri-component/-/decode-uri-component-0.2.0.tgz#eb3913333458775cb84cd1a1fae062106bb87545"
   integrity sha1-6zkTMzRYd1y4TNGh+uBiEGu4dUU=
 
-deep-eql@^0.1.3:
-  version "0.1.3"
-  resolved "https://registry.yarnpkg.com/deep-eql/-/deep-eql-0.1.3.tgz#ef558acab8de25206cd713906d74e56930eb69f2"
-  integrity sha1-71WKyrjeJSBs1xOQbXTlaTDrafI=
+deep-eql@^3.0.1:
+  version "3.0.1"
+  resolved "https://registry.yarnpkg.com/deep-eql/-/deep-eql-3.0.1.tgz#dfc9404400ad1c8fe023e7da1df1c147c4b444df"
+  integrity sha512-+QeIQyN5ZuO+3Uk5DYh6/1eKO0m0YmJFGNmFHGACpf1ClL1nmlV/p4gNgbl2pJGxgXb4faqo6UE+M5ACEMyVcw==
   dependencies:
-    type-detect "0.1.1"
+    type-detect "^4.0.0"
 
 deep-extend@^0.6.0:
   version "0.6.0"
@@ -2671,6 +2679,11 @@ generate-object-property@^1.1.0:
   dependencies:
     is-property "^1.0.0"
 
+get-func-name@^2.0.0:
+  version "2.0.0"
+  resolved "https://registry.yarnpkg.com/get-func-name/-/get-func-name-2.0.0.tgz#ead774abee72e20409433a066366023dd6887a41"
+  integrity sha1-6td0q+5y4gQJQzoGY2YCPdaIekE=
+
 get-stdin@^6.0.0:
   version "6.0.0"
   resolved "https://registry.yarnpkg.com/get-stdin/-/get-stdin-6.0.0.tgz#9e09bf712b360ab9225e812048f71fde9c89657b"
@@ -4761,6 +4774,11 @@ path-type@^2.0.0:
   dependencies:
     pify "^2.0.0"
 
+pathval@^1.1.0:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/pathval/-/pathval-1.1.0.tgz#b942e6d4bde653005ef6b71361def8727d0645e0"
+  integrity sha1-uULm1L3mUwBe9rcTYd74cn0GReA=
+
 pbkdf2-compat@2.0.1:
   version "2.0.1"
   resolved "https://registry.yarnpkg.com/pbkdf2-compat/-/pbkdf2-compat-2.0.1.tgz#b6e0c8fa99494d94e0511575802a59a5c142f288"
@@ -5997,15 +6015,10 @@ type-check@~0.3.2:
   dependencies:
     prelude-ls "~1.1.2"
 
-type-detect@0.1.1:
-  version "0.1.1"
-  resolved "https://registry.yarnpkg.com/type-detect/-/type-detect-0.1.1.tgz#0ba5ec2a885640e470ea4e8505971900dac58822"
-  integrity sha1-C6XsKohWQORw6k6FBZcZANrFiCI=
-
-type-detect@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/type-detect/-/type-detect-1.0.0.tgz#762217cc06db258ec48908a1298e8b95121e8ea2"
-  integrity sha1-diIXzAbbJY7EiQihKY6LlRIejqI=
+type-detect@^4.0.0, type-detect@^4.0.5:
+  version "4.0.8"
+  resolved "https://registry.yarnpkg.com/type-detect/-/type-detect-4.0.8.tgz#7646fb5f18871cfbb7749e69bd39a6388eb7450c"
+  integrity sha512-0fr/mIH1dlO+x7TlcMy+bIDqKPsw/70tVyeHW787goQjhmqaZe10uwLujubK9q9Lg6Fiho1KUKDYz0Z7k7g5/g==
 
 type-is@~1.6.16:
   version "1.6.16"