diff --git a/src/nvim/edit.c b/src/nvim/edit.c
index 61742938dd..d6373f9c49 100644
--- a/src/nvim/edit.c
+++ b/src/nvim/edit.c
@@ -2133,7 +2133,8 @@ void insertchar(int c, int flags, int second_indent)
       i -= middle_len;
 
       // Check some expected things before we go on
-      if (i >= 0 && (uint8_t)lead_end[end_len - 1] == end_comment_pending) {
+      if (i >= 0 && end_len > 0
+          && (uint8_t)lead_end[end_len - 1] == end_comment_pending) {
         // Backspace over all the stuff we want to replace
         backspace_until_column(i);