diff --git a/src/lib/components/Keyboard.js b/src/lib/components/Keyboard.js
index 1f201603..99b56b4f 100644
--- a/src/lib/components/Keyboard.js
+++ b/src/lib/components/Keyboard.js
@@ -1285,12 +1285,15 @@ class SimpleKeyboard {
          */
         const buttonHasContainerStart =
           !disableRowButtonContainers &&
-          button.includes("[") &&
-          button.length > 1;
+          typeof button === "string" &&
+          button.length > 1 &&
+          button.indexOf("[") === 0;
+
         const buttonHasContainerEnd =
           !disableRowButtonContainers &&
-          button.includes("]") &&
-          button.length > 1;
+          typeof button === "string" &&
+          button.length > 1 &&
+          button.indexOf("]") === button.length - 1;
 
         /**
          * Save container start index, if applicable