diff --git a/lisp/progmodes/ruby-ts-mode.el b/lisp/progmodes/ruby-ts-mode.el
index f0337775d51..c3c77d68e9a 100644
--- a/lisp/progmodes/ruby-ts-mode.el
+++ b/lisp/progmodes/ruby-ts-mode.el
@@ -546,6 +546,12 @@ ruby-ts--indent-rules
            ((n-p-gp nil nil "regex") no-indent 0)
            ((parent-is "regex") no-indent 0)
 
+           ;; Incomplete buffer state, better not reindent.
+           ((and (parent-is "ERROR")
+                 (or (node-is ,ruby-ts--class-or-module-regex)
+                     (node-is "\\`def\\'")))
+            no-indent 0)
+
            ;; if then else elseif notes:
            ;;
            ;;   1. The "then" starts at the end of the line that ends