diff --git a/package.json b/package.json
index 1cb21e8b2..c6130ab68 100644
--- a/package.json
+++ b/package.json
@@ -77,6 +77,7 @@
     "async": "^2.3.0",
     "babel-core": "^6.24.1",
     "babel-loader": "^6.4.1",
+    "babel-plugin-transform-remove-strict-mode": "^0.0.2",
     "babel-preset-env": "^1.4.0",
     "browserify": "~14.3.0",
     "clone": "^2.1.1",
diff --git a/src/diagrams/classDiagram/parser/classDiagram.js b/src/diagrams/classDiagram/parser/classDiagram.js
index 1a3afa254..83908059d 100644
--- a/src/diagrams/classDiagram/parser/classDiagram.js
+++ b/src/diagrams/classDiagram/parser/classDiagram.js
@@ -202,15 +202,14 @@ var parser = (function () {
         vstack.length = vstack.length - n
         lstack.length = lstack.length - n
       }
-      _token_stack:
-        var lex = function () {
-          var token
-          token = lexer.lex() || EOF
-          if (typeof token !== 'number') {
+      var lex = function () {
+        var token
+        token = lexer.lex() || EOF
+        if (typeof token !== 'number') {
             token = self.symbols_[token] || token
           }
-          return token
-        }
+        return token
+      }
       var symbol, preErrorSymbol, state, action, a, r, yyval = {}, p, len, newState, expected
       while (true) {
         state = stack[stack.length - 1]
diff --git a/src/diagrams/example/parser/example.js b/src/diagrams/example/parser/example.js
index a5a63c354..d7b9c42ec 100644
--- a/src/diagrams/example/parser/example.js
+++ b/src/diagrams/example/parser/example.js
@@ -142,8 +142,7 @@ var parser = (function () {
         vstack.length = vstack.length - n
         lstack.length = lstack.length - n
       }
-      _token_stack:
-        var lex = function () {
+      var lex = function () {
           var token
           token = lexer.lex() || EOF
           if (typeof token !== 'number') {
diff --git a/src/diagrams/flowchart/parser/dot.js b/src/diagrams/flowchart/parser/dot.js
index bd722b5a6..134179286 100644
--- a/src/diagrams/flowchart/parser/dot.js
+++ b/src/diagrams/flowchart/parser/dot.js
@@ -182,8 +182,7 @@ var parser = (function () {
         vstack.length = vstack.length - n
         lstack.length = lstack.length - n
       }
-      _token_stack:
-        var lex = function () {
+      var lex = function () {
           var token
           token = lexer.lex() || EOF
           if (typeof token !== 'number') {
diff --git a/src/diagrams/flowchart/parser/flow.js b/src/diagrams/flowchart/parser/flow.js
index 8d5a6cf55..2e069ecd7 100644
--- a/src/diagrams/flowchart/parser/flow.js
+++ b/src/diagrams/flowchart/parser/flow.js
@@ -347,8 +347,7 @@ var parser = (function () {
         vstack.length = vstack.length - n
         lstack.length = lstack.length - n
       }
-      _token_stack:
-        var lex = function () {
+      var lex = function () {
           var token
           token = lexer.lex() || EOF
           if (typeof token !== 'number') {
diff --git a/src/diagrams/gantt/parser/gantt.js b/src/diagrams/gantt/parser/gantt.js
index 888fe13ce..cc2d2af61 100644
--- a/src/diagrams/gantt/parser/gantt.js
+++ b/src/diagrams/gantt/parser/gantt.js
@@ -155,7 +155,6 @@ var parser = (function () {
         vstack.length = vstack.length - n
         lstack.length = lstack.length - n
       }
-      _token_stack:
       var lex = function () {
         var token
         token = lexer.lex() || EOF
diff --git a/src/diagrams/gitGraph/parser/gitGraph.js b/src/diagrams/gitGraph/parser/gitGraph.js
index e0177dbdd..15aba76ea 100644
--- a/src/diagrams/gitGraph/parser/gitGraph.js
+++ b/src/diagrams/gitGraph/parser/gitGraph.js
@@ -181,8 +181,7 @@ var parser = (function () {
         vstack.length = vstack.length - n
         lstack.length = lstack.length - n
       }
-      _token_stack:
-        var lex = function () {
+      var lex = function () {
           var token
           token = lexer.lex() || EOF
           if (typeof token !== 'number') {
diff --git a/src/diagrams/sequenceDiagram/parser/sequenceDiagram.js b/src/diagrams/sequenceDiagram/parser/sequenceDiagram.js
index 372ad5f8e..77a16a39a 100644
--- a/src/diagrams/sequenceDiagram/parser/sequenceDiagram.js
+++ b/src/diagrams/sequenceDiagram/parser/sequenceDiagram.js
@@ -252,8 +252,7 @@ var parser = (function () {
         vstack.length = vstack.length - n
         lstack.length = lstack.length - n
       }
-      _token_stack:
-        var lex = function () {
+      var lex = function () {
           var token
           token = lexer.lex() || EOF
           if (typeof token !== 'number') {
diff --git a/todo.md b/todo.md
index 03caf08fa..358a48d79 100644
--- a/todo.md
+++ b/todo.md
@@ -9,3 +9,6 @@
     - dist
     - docs
 - 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
diff --git a/webpack.config.base.js b/webpack.config.base.js
index 3b8acb01e..efc9b9c07 100644
--- a/webpack.config.base.js
+++ b/webpack.config.base.js
@@ -25,6 +25,9 @@ export const webConfig = () => {
                     'browsers': ['last 3 versions']
                   }
                 }]
+              ],
+              plugins: [
+                'transform-remove-strict-mode'
               ]
             }
           }
diff --git a/yarn.lock b/yarn.lock
index f18022617..d8d15cc5c 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -909,6 +909,10 @@ babel-plugin-transform-regenerator@^6.22.0, babel-plugin-transform-regenerator@^
   dependencies:
     regenerator-transform "0.9.11"
 
+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-runtime@^6.15.0:
   version "6.23.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-transform-runtime/-/babel-plugin-transform-runtime-6.23.0.tgz#88490d446502ea9b8e7efb0fe09ec4d99479b1ee"