1 files changed, 1 insertions, 0 deletions

diff --git a/src/lisp.h b/src/lisp.h
index dce61c165cf..faf5a4ad407 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3413,6 +3413,7 @@ extern void syms_of_syntax (void);
 
 /* Defined in fns.c.  */
 enum { NEXT_ALMOST_PRIME_LIMIT = 11 };
+extern ptrdiff_t list_length (Lisp_Object);
 extern EMACS_INT next_almost_prime (EMACS_INT) ATTRIBUTE_CONST;
 extern Lisp_Object larger_vector (Lisp_Object, ptrdiff_t, ptrdiff_t);
 extern void sweep_weak_hash_tables (void);