diff --git a/fetch.js b/fetch.js
index 3c02d57e..f88488cd 100644
--- a/fetch.js
+++ b/fetch.js
@@ -1,9 +1,13 @@
+var global = (function(self) {
+  return self
+  // eslint-disable-next-line no-invalid-this
+})(typeof self !== 'undefined' ? self : this)
 var support = {
-  searchParams: 'URLSearchParams' in self,
-  iterable: 'Symbol' in self && 'iterator' in Symbol,
+  searchParams: 'URLSearchParams' in global,
+  iterable: 'Symbol' in global && 'iterator' in Symbol,
   blob:
-    'FileReader' in self &&
-    'Blob' in self &&
+    'FileReader' in global &&
+    'Blob' in global &&
     (function() {
       try {
         new Blob()
@@ -12,8 +16,8 @@ var support = {
         return false
       }
     })(),
-  formData: 'FormData' in self,
-  arrayBuffer: 'ArrayBuffer' in self
+  formData: 'FormData' in global,
+  arrayBuffer: 'ArrayBuffer' in global
 }
 
 function isDataView(obj) {
@@ -435,7 +439,7 @@ Response.redirect = function(url, status) {
   return new Response(null, {status: status, headers: {location: url}})
 }
 
-export var DOMException = self.DOMException
+export var DOMException = global.DOMException
 try {
   new DOMException()
 } catch (err) {
@@ -496,7 +500,7 @@ export function fetch(input, init) {
 
     function fixUrl(url) {
       try {
-        return url === '' && self.location.href ? self.location.href : url
+        return url === '' && global.location.href ? global.location.href : url
       } catch (e) {
         return url
       }
@@ -543,9 +547,9 @@ export function fetch(input, init) {
 
 fetch.polyfill = true
 
-if (!self.fetch) {
-  self.fetch = fetch
-  self.Headers = Headers
-  self.Request = Request
-  self.Response = Response
+if (!global.fetch) {
+  global.fetch = fetch
+  global.Headers = Headers
+  global.Request = Request
+  global.Response = Response
 }
diff --git a/rollup.config.js b/rollup.config.js
index d4297335..3ed622ca 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -3,6 +3,7 @@ export default {
   output: {
     file: 'dist/fetch.umd.js',
     format: 'umd',
-    name: 'WHATWGFetch'
+    name: 'WHATWGFetch',
+    strict: false
   }
 }