diff --git a/lib/kadm5/sample_passwd_check.c b/lib/kadm5/sample_passwd_check.c
index f19f5f7d7..ca5123bf4 100644
--- a/lib/kadm5/sample_passwd_check.c
+++ b/lib/kadm5/sample_passwd_check.c
@@ -36,6 +36,8 @@
 #include <stdlib.h>
 #include <krb5.h>
 
+const char* check_length(krb5_context, krb5_principal, krb5_data *);
+
 /* specify the api-version this library conforms to */
 
 int version = 0;