diff --git a/docs/Theming.md b/docs/Theming.md
index e6d77ed360f..8d1e4530744 100644
--- a/docs/Theming.md
+++ b/docs/Theming.md
@@ -661,7 +661,7 @@ import { withRouter } from 'react-router-dom';
 const MyMenu = ({ resources, onMenuClick, logout }) => (
     <div>
         {resources.map(resource => (
-            <MenuItemLink to={`/${resource.name}`} primaryText={resource.name} onClick={onMenuClick} />
+            <MenuItemLink key={resource.name} to={`/${resource.name}`} primaryText={resource.name} onClick={onMenuClick} />
         ))}
         <MenuItemLink to="/custom-route" primaryText="Miscellaneous" onClick={onMenuClick} />
         <Responsive
@@ -745,7 +745,7 @@ const styles = {
 const MyMenu = ({ classes, resources, onMenuClick, logout }) => (
     <div>
         {resources.map(resource => (
-            <MenuItemLink classes={classes} to={`/${resource.name}`} primaryText={resource.name} onClick={onMenuClick} />
+            <MenuItemLink classes={classes} key={resource.name} to={`/${resource.name}`} primaryText={resource.name} onClick={onMenuClick} />
         ))}
         <MenuItemLink classes={classes} to="/custom-route" primaryText="Miscellaneous" onClick={onMenuClick} />
         <Responsive