diff --git a/src/lisp/lib/std.h b/src/lisp/lib/std.h
index 5162bab..9070de8 100644
--- a/src/lisp/lib/std.h
+++ b/src/lisp/lib/std.h
@@ -4,6 +4,7 @@
 #include "../lisp.h"
 
 value_t l_plus(value_t a, value_t b);
+value_t l_printval(value_t val);
 
 void add_function(struct environment *env, char *name, void *func, int nargs, enum namespace ns);
 void load_std(struct environment *env);