1 files changed, 1 insertions, 1 deletions

diff --git a/lisp/calc/calc-prog.el b/lisp/calc/calc-prog.el
index 230b0f6a6c5..0a24fbf574c 100644
--- a/lisp/calc/calc-prog.el
+++ b/lisp/calc/calc-prog.el
@@ -702,7 +702,7 @@
                                (get func 'calc-user-defn)))
                     (kys (concat "z" (char-to-string (car def))))
                     (intcmd (symbol-name (cdr def)))
-                    (algcmd (substring (symbol-name func) 9)))
+                    (algcmd (if func (substring (symbol-name func) 9) "")))
                (if (and defn (calc-valid-formula-func func))
                    (let ((niceexpr (math-format-nice-expr defn (frame-width))))
                      (calc-wrapper