diff --git a/karma.conf.js b/karma.conf.js
index b6b7b20f9..26dc5920d 100644
--- a/karma.conf.js
+++ b/karma.conf.js
@@ -32,6 +32,7 @@ module.exports = function (config) {
         rules: [
           {
             test: /\.js$/,
+            exclude: /node_modules/,
             use: {
               loader: 'babel-loader',
               options: {
@@ -41,9 +42,6 @@ module.exports = function (config) {
                       'browsers': ['last 3 versions']
                     }
                   }]
-                ],
-                plugins: [
-                  'transform-remove-strict-mode'
                 ]
               }
             }
diff --git a/package.json b/package.json
index 7207c7e1e..62dfcf51e 100644
--- a/package.json
+++ b/package.json
@@ -58,7 +58,6 @@
     "async": "^2.5.0",
     "babel-core": "^6.26.0",
     "babel-loader": "^7.1.2",
-    "babel-plugin-transform-remove-strict-mode": "^0.0.2",
     "babel-preset-env": "^1.6.0",
     "babel-preset-es2015": "^6.24.1",
     "clone": "^2.1.1",
diff --git a/src/utils.spec.js b/src/utils.spec.js
index a978b9b38..2b31c9364 100644
--- a/src/utils.spec.js
+++ b/src/utils.spec.js
@@ -87,16 +87,15 @@ describe('when cloning CSS ', function () {
   }
 
   function addMermaidSVGwithStyleToDocument () {
-    var styleSheetCount = document.styleSheets.length
     var svg = document.createElement('svg')
     svg.setAttribute('id', 'mermaid-03')
     var s = document.createElement('style')
     s.setAttribute('type', 'text/css')
     s.setAttribute('title', 'mermaid-svg-internal-css')
     s.innerHTML = '#mermaid-05 .node2 { stroke:#eee; }\n.node-square { stroke:#bfe; }\n'
+    s.title = 'mermaid-svg-internal-css'
     svg.appendChild(s)
     document.body.appendChild(svg)
-    document.styleSheets[styleSheetCount].title = 'mermaid-svg-internal-css'
   }
 
   it('should handle errors thrown when accessing CSS rules', function () {
@@ -104,7 +103,7 @@ describe('when cloning CSS ', function () {
     svg.setAttribute('id', 'mermaid-01')
 
     // Firefox throws a SecurityError when trying to access cssRules
-    document.styleSheets[document.styleSheets.length++] = {
+    document.styleSheets[document.styleSheets.length] = {
       get cssRules () { throw new Error('SecurityError') }
     }
 
diff --git a/todo.md b/todo.md
index f3b5dde3c..1d52854bf 100644
--- a/todo.md
+++ b/todo.md
@@ -3,9 +3,6 @@
     - Problem is it's for d3 v4 only
 - Make node console output colors like Chrome console
 - What's the correct way to change logLevel as an end user?
-- d3 v3 doesn't support 'use strict'
-    - babel-plugin-transform-remove-strict-mode
-        - need to remove it after upgrading to d3 v4
 - Fix CodeClimate
 - What is live-server ?
 - Get familar with jison
diff --git a/webpack.config.base.js b/webpack.config.base.js
index f48548092..ede2ce7d3 100644
--- a/webpack.config.base.js
+++ b/webpack.config.base.js
@@ -36,9 +36,6 @@ export const webConfig = () => {
                     'browsers': ['last 3 versions']
                   }
                 }]
-              ],
-              plugins: [
-                'transform-remove-strict-mode'
               ]
             }
           }
diff --git a/yarn.lock b/yarn.lock
index 3dcb4069a..6696b9f28 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -708,10 +708,6 @@ babel-plugin-transform-regenerator@^6.24.1:
   dependencies:
     regenerator-transform "^0.10.0"
 
-babel-plugin-transform-remove-strict-mode@^0.0.2:
-  version "0.0.2"
-  resolved "https://registry.yarnpkg.com/babel-plugin-transform-remove-strict-mode/-/babel-plugin-transform-remove-strict-mode-0.0.2.tgz#913685aab95439f3a0ed88e588fbd5e997890579"
-
 babel-plugin-transform-strict-mode@^6.24.1:
   version "6.24.1"
   resolved "https://registry.yarnpkg.com/babel-plugin-transform-strict-mode/-/babel-plugin-transform-strict-mode-6.24.1.tgz#d5faf7aa578a65bbe591cf5edae04a0c67020758"