diff --git a/accessible/tests/browser/text/browser_text_caret.js b/accessible/tests/browser/text/browser_text_caret.js
index e0cea334d684..29d7ede33295 100644
--- a/accessible/tests/browser/text/browser_text_caret.js
+++ b/accessible/tests/browser/text/browser_text_caret.js
@@ -278,6 +278,17 @@ addAccessibleTask(
       kOk,
       kOk
     );
+    testTextAtOffset(
+      kCaretOffset,
+      BOUNDARY_CLUSTER,
+      "",
+      6,
+      6,
+      textarea,
+      kOk,
+      kOk,
+      kOk
+    );
     testTextAtOffset(
       kCaretOffset,
       BOUNDARY_WORD_START,
diff --git a/accessible/tests/mochitest/text.js b/accessible/tests/mochitest/text.js
index 5fad7d5ebbb5..f1bf661caeaa 100644
--- a/accessible/tests/mochitest/text.js
+++ b/accessible/tests/mochitest/text.js
@@ -826,6 +826,8 @@ function boundaryToString(aBoundaryType) {
       return "line end";
     case BOUNDARY_PARAGRAPH:
       return "paragraph";
+    case BOUNDARY_CLUSTER:
+      return "cluster";
   }
   return "unknown";
 }