diff --git a/package-lock.json b/package-lock.json
index 332d8fb1b..eb7b05bd1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "handlebars",
-  "version": "4.5.0",
+  "version": "4.5.1",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -324,6 +324,12 @@
       "integrity": "sha1-8S4PPF13sLHN2RRpQuTpbB5N1SU=",
       "dev": true
     },
+    "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
+    },
     "assign-symbols": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/assign-symbols/-/assign-symbols-1.0.0.tgz",
@@ -985,6 +991,20 @@
         "lazy-cache": "^1.0.3"
       }
     },
+    "chai": {
+      "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",
       "resolved": "https://registry.npmjs.org/chalk/-/chalk-1.1.3.tgz",
@@ -1004,6 +1024,12 @@
       "integrity": "sha1-tUc7M9yXxCTl2Y3IfVXU2KKci/I=",
       "dev": true
     },
+    "check-error": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/check-error/-/check-error-1.0.2.tgz",
+      "integrity": "sha1-V00xLt2Iu13YkS6Sht1sCu1KrII=",
+      "dev": true
+    },
     "chokidar": {
       "version": "1.5.2",
       "resolved": "https://registry.npmjs.org/chokidar/-/chokidar-1.5.2.tgz",
@@ -1467,6 +1493,15 @@
       "integrity": "sha1-6zkTMzRYd1y4TNGh+uBiEGu4dUU=",
       "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"
+      }
+    },
     "deep-is": {
       "version": "0.1.3",
       "resolved": "https://registry.npmjs.org/deep-is/-/deep-is-0.1.3.tgz",
@@ -1619,6 +1654,12 @@
       "integrity": "sha1-gAwN0eCov7yVg1wgKtIg/jF+WhI=",
       "dev": true
     },
+    "dirty-chai": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/dirty-chai/-/dirty-chai-2.0.1.tgz",
+      "integrity": "sha512-ys79pWKvDMowIDEPC6Fig8d5THiC0DJ2gmTeGzVAoEH18J8OzLud0Jh7I9IWg3NSk8x2UocznUuFmfHCXYZx9w==",
+      "dev": true
+    },
     "doctrine": {
       "version": "2.1.0",
       "resolved": "https://registry.npmjs.org/doctrine/-/doctrine-2.1.0.tgz",
@@ -3287,6 +3328,12 @@
       "integrity": "sha1-+Xj6TJDR3+f/LWvtoqUV5xO9z0o=",
       "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-stdin": {
       "version": "4.0.1",
       "resolved": "https://registry.npmjs.org/get-stdin/-/get-stdin-4.0.1.tgz",
@@ -6234,6 +6281,12 @@
         "pinkie-promise": "^2.0.0"
       }
     },
+    "pathval": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/pathval/-/pathval-1.1.0.tgz",
+      "integrity": "sha1-uULm1L3mUwBe9rcTYd74cn0GReA=",
+      "dev": true
+    },
     "pbkdf2-compat": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/pbkdf2-compat/-/pbkdf2-compat-2.0.1.tgz",
@@ -8162,6 +8215,12 @@
         "prelude-ls": "~1.1.2"
       }
     },
+    "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
+    },
     "type-is": {
       "version": "1.6.16",
       "resolved": "https://registry.npmjs.org/type-is/-/type-is-1.6.16.tgz",
diff --git a/package.json b/package.json
index d753c9b2a..fdac39237 100644
--- a/package.json
+++ b/package.json
@@ -34,6 +34,8 @@
     "babel-loader": "^5.0.0",
     "babel-runtime": "^5.1.10",
     "benchmark": "~1.0",
+    "chai": "^4.2.0",
+    "dirty-chai": "^2.0.1",
     "dtslint": "^0.5.5",
     "dustjs-linkedin": "^2.0.2",
     "eco": "~1.1.0-rc-3",
diff --git a/spec/env/node.js b/spec/env/node.js
index 881609d2e..8b97c4d53 100644
--- a/spec/env/node.js
+++ b/spec/env/node.js
@@ -1,5 +1,11 @@
 require('./common');
 
+var chai = require('chai');
+var dirtyChai = require('dirty-chai');
+
+chai.use(dirtyChai);
+global.expect = chai.expect;
+
 global.Handlebars = require('../../lib');
 
 global.CompilerContext = {
diff --git a/spec/index.html b/spec/index.html
index 5db2146ad..3528b78d6 100644
--- a/spec/index.html
+++ b/spec/index.html
@@ -20,6 +20,8 @@
       }
     </script>
     <script src="/node_modules/mocha/mocha.js"></script>
+    <script src="/node_modules/chai/chai.js"></script>
+    <script src="/node_modules/dirty-chai/lib/dirty-chai.js"></script>
     <script>
       mocha.setup('bdd');
     </script>