diff --git a/config.go b/config.go
index 800b7ba..33f4b89 100644
--- a/config.go
+++ b/config.go
@@ -5,6 +5,7 @@ package zoopb
 
 import (
 	"errors"
+	"fmt"
 	"os"
 	"path/filepath"
 
@@ -15,6 +16,9 @@ import (
 // writes out the cluster information it seperate files
 // to make it humanly possible to hand edit things as needed
 func (m *Machines) ConfigSave() error {
+	if m == nil {
+		return fmt.Errorf("ConfigSave() machines == n")
+	}
 	data, err := m.Marshal()
 	if err != nil {
 		log.Info("proto.Marshal() failed len", len(data), err)