diff --git a/manifests/kerberos/krb5_conf.pp b/manifests/kerberos/krb5_conf.pp
index e634862a206c2172752467386972e01fed3d3475..6cf0c4570b50b3e2862a256320d1f7ad37956ce6 100644
--- a/manifests/kerberos/krb5_conf.pp
+++ b/manifests/kerberos/krb5_conf.pp
@@ -206,7 +206,7 @@ define base::kerberos::krb5_conf (
     }
     'custom': {
       # Verify that the needed parameters are set.
-      if (length($kdcs) == 0) {
+      if (size($kdcs) == 0) {
         fail("when using a 'custom' environment you must define the kdc's")
       }
       if ($master_kdc == undef) {