From 56cec2b83713076b9c27751ca5c0c5e07943b6a8 Mon Sep 17 00:00:00 2001
From: Arno Gourdol <arno@arno.org>
Date: Tue, 23 May 2023 07:55:22 -0700
Subject: [PATCH] fix: fixed #1981

---
 src/editor-mathfield/keyboard-input.ts | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/editor-mathfield/keyboard-input.ts b/src/editor-mathfield/keyboard-input.ts
index cb8e2a9e9..33b139efc 100644
--- a/src/editor-mathfield/keyboard-input.ts
+++ b/src/editor-mathfield/keyboard-input.ts
@@ -652,7 +652,12 @@ function insertMathModeChar(
   if (mathfield.adoptStyle !== 'none') {
     // If adding an alphabetic character, and the neighboring atom is an
     // alphanumeric character, use the same variant/variantStyle (\mathit, \mathrm...)
-    const sibling = mathfield.adoptStyle === 'left' ? atom : atom.rightSibling;
+    const sibling =
+      mathfield.adoptStyle === 'left'
+        ? atom
+        : atom.parent
+        ? atom.rightSibling
+        : null;
     if (
       sibling?.type === 'mord' &&
       /[a-zA-Z0-9]/.test(sibling.value) &&