diff --git a/iucvterm/include/iucvterm/functions.h b/iucvterm/include/iucvterm/functions.h
index 4f6ad809..90fe4938 100644
--- a/iucvterm/include/iucvterm/functions.h
+++ b/iucvterm/include/iucvterm/functions.h
@@ -62,7 +62,7 @@ extern ssize_t __write(int, const void*, size_t);
 extern int strmatch(const char *, const char *);
 extern int is_regex_valid(const char *);
 extern int is_client_allowed(const char *, const struct iucvterm_cfg *);
-extern void userid_cpy(char [8], const char [8]);
+extern void userid_cpy(char [9], const char [8]);
 
 extern void iucv_msg_error(const char *, uint32_t);
 extern void program_error(const char *, const char *);