diff --git a/dist/index.js b/dist/index.js
index 5443c412..0ac74b9f 100644
--- a/dist/index.js
+++ b/dist/index.js
@@ -80,7 +80,7 @@
                 canceled: !1
             }, args);
         }, exports.MutationObserver = function() {
-            for (var prefixes = [ "", "WebKit", "Moz", "O", "Ms" ], i = 0; i < prefixes.length; i++) {
+            if ("undefined" != typeof window) for (var prefixes = [ "", "WebKit", "Moz", "O", "Ms" ], i = 0; i < prefixes.length; i++) {
                 var name = prefixes[i] + "MutationObserver";
                 if (name in window) return window[name];
             }
diff --git a/dist/ssr.index.js b/dist/ssr.index.js
index 6eef97e7..9522af1f 100644
--- a/dist/ssr.index.js
+++ b/dist/ssr.index.js
@@ -80,7 +80,7 @@
                 canceled: !1
             }, args);
         }, exports.MutationObserver = function() {
-            for (var prefixes = [ "", "WebKit", "Moz", "O", "Ms" ], i = 0; i < prefixes.length; i++) {
+            if ("undefined" != typeof window) for (var prefixes = [ "", "WebKit", "Moz", "O", "Ms" ], i = 0; i < prefixes.length; i++) {
                 var name = prefixes[i] + "MutationObserver";
                 if (name in window) return window[name];
             }
diff --git a/dist/ssr.nocss.js b/dist/ssr.nocss.js
index a02fb33a..f244f148 100644
--- a/dist/ssr.nocss.js
+++ b/dist/ssr.nocss.js
@@ -80,7 +80,7 @@
                 canceled: !1
             }, args);
         }, exports.MutationObserver = function() {
-            for (var prefixes = [ "", "WebKit", "Moz", "O", "Ms" ], i = 0; i < prefixes.length; i++) {
+            if ("undefined" != typeof window) for (var prefixes = [ "", "WebKit", "Moz", "O", "Ms" ], i = 0; i < prefixes.length; i++) {
                 var name = prefixes[i] + "MutationObserver";
                 if (name in window) return window[name];
             }
diff --git a/src/util.js b/src/util.js
index 936b0bb5..cce3b61c 100644
--- a/src/util.js
+++ b/src/util.js
@@ -32,7 +32,7 @@ export const createModalEvent = (args = {}) => {
 }
 
 export const MutationObserver = (() => {
-  if (typeof window !== 'undefined')) {
+  if (typeof window !== 'undefined') {
     const prefixes = ['', 'WebKit', 'Moz', 'O', 'Ms']
 
     for (let i = 0; i < prefixes.length; i++) {