diff --git a/package.json b/package.json
index 792e246..f88e8d5 100644
--- a/package.json
+++ b/package.json
@@ -65,7 +65,7 @@
     "babel-preset-stage-1": "^6.22.0",
     "babel-register": "^6.23.0",
     "babel-runtime": "^6.23.0",
-    "chai": "^3.5.0",
+    "chai": "^4.0.0",
     "codecov": "^2.3.0",
     "copy": "^0.3.0",
     "eslint": "^3.15.0",
diff --git a/yarn.lock b/yarn.lock
index 4d0dcb8..0976ad6 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -1190,13 +1190,16 @@ center-align@^0.1.1:
     align-text "^0.1.3"
     lazy-cache "^1.0.3"
 
-chai@^3.5.0:
-  version "3.5.0"
-  resolved "https://registry.yarnpkg.com/chai/-/chai-3.5.0.tgz#4d02637b067fe958bdbfdd3a40ec56fef7373247"
+chai@^4.0.0:
+  version "4.1.2"
+  resolved "https://registry.yarnpkg.com/chai/-/chai-4.1.2.tgz#0f64584ba642f0f2ace2806279f4f06ca23ad73c"
   dependencies:
     assertion-error "^1.0.1"
-    deep-eql "^0.1.3"
-    type-detect "^1.0.0"
+    check-error "^1.0.1"
+    deep-eql "^3.0.0"
+    get-func-name "^2.0.0"
+    pathval "^1.0.0"
+    type-detect "^4.0.0"
 
 chalk@2.3.0, chalk@^2.0.0, chalk@^2.0.1, chalk@^2.1.0, chalk@^2.3.0:
   version "2.3.0"
@@ -1216,6 +1219,10 @@ chalk@^1.0.0, chalk@^1.1.0, chalk@^1.1.1, chalk@^1.1.3:
     strip-ansi "^3.0.0"
     supports-color "^2.0.0"
 
+check-error@^1.0.1:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/check-error/-/check-error-1.0.2.tgz#574d312edd88bb5dd8912e9286dd6c0aed4aac82"
+
 chokidar@^1.4.3, chokidar@^1.6.1:
   version "1.6.1"
   resolved "https://registry.yarnpkg.com/chokidar/-/chokidar-1.6.1.tgz#2f4447ab5e96e50fb3d789fd90d4c72e0e4c70c2"
@@ -1573,11 +1580,11 @@ decompress-response@^3.3.0:
   dependencies:
     mimic-response "^1.0.0"
 
-deep-eql@^0.1.3:
-  version "0.1.3"
-  resolved "https://registry.yarnpkg.com/deep-eql/-/deep-eql-0.1.3.tgz#ef558acab8de25206cd713906d74e56930eb69f2"
+deep-eql@^3.0.0:
+  version "3.0.1"
+  resolved "https://registry.yarnpkg.com/deep-eql/-/deep-eql-3.0.1.tgz#dfc9404400ad1c8fe023e7da1df1c147c4b444df"
   dependencies:
-    type-detect "0.1.1"
+    type-detect "^4.0.0"
 
 deep-extend@~0.4.0:
   version "0.4.1"
@@ -2230,6 +2237,10 @@ get-caller-file@^1.0.1:
   version "1.0.2"
   resolved "https://registry.yarnpkg.com/get-caller-file/-/get-caller-file-1.0.2.tgz#f702e63127e7e231c160a80c1554acb70d5047e5"
 
+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"
+
 get-stdin@5.0.1:
   version "5.0.1"
   resolved "https://registry.npmjs.org/get-stdin/-/get-stdin-5.0.1.tgz#122e161591e21ff4c52530305693f20e6393a398"
@@ -3894,6 +3905,10 @@ path-type@^3.0.0:
   dependencies:
     pify "^3.0.0"
 
+pathval@^1.0.0:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/pathval/-/pathval-1.1.0.tgz#b942e6d4bde653005ef6b71361def8727d0645e0"
+
 pause-stream@0.0.11:
   version "0.0.11"
   resolved "https://registry.yarnpkg.com/pause-stream/-/pause-stream-0.0.11.tgz#fe5a34b0cbce12b5aa6a2b403ee2e73b602f1445"
@@ -4860,13 +4875,9 @@ 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"
-
-type-detect@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/type-detect/-/type-detect-1.0.0.tgz#762217cc06db258ec48908a1298e8b95121e8ea2"
+type-detect@^4.0.0:
+  version "4.0.5"
+  resolved "https://registry.yarnpkg.com/type-detect/-/type-detect-4.0.5.tgz#d70e5bc81db6de2a381bcaca0c6e0cbdc7635de2"
 
 typedarray@^0.0.6:
   version "0.0.6"