diff --git a/src/components/components/AddComponent.js b/src/components/components/AddComponent.js
index 361e2f67..2eef289e 100644
--- a/src/components/components/AddComponent.js
+++ b/src/components/components/AddComponent.js
@@ -99,7 +99,7 @@ export default class AddComponent extends React.Component {
  */
 function isComponentInstanced(entity, componentName) {
   for (var component in entity.components) {
-    if (component.substr(0, component.indexOf('__')) === componentName) {
+    if (component.substring(0, component.indexOf('__')) === componentName) {
       return true;
     }
   }