diff --git a/pit.go b/pit.go
index 22871309..e6594bf0 100644
--- a/pit.go
+++ b/pit.go
@@ -17,11 +17,14 @@ type PointInTime struct {
 }
 
 // NewPointInTime creates a new PointInTime.
-func NewPointInTime(id, keepAlive string) *PointInTime {
-	return &PointInTime{
+func NewPointInTime(id string, keepAlive ...string) *PointInTime {
+	pit := &PointInTime{
 		Id:        id,
-		KeepAlive: keepAlive,
 	}
+	if len(keepAlive) > 1 {
+		pit.KeepAlive = keepAlive[0]
+	}
+	return pit
 }
 
 // Source generates the JSON serializable fragment for the PointInTime.
@@ -29,8 +32,13 @@ func (pit *PointInTime) Source() (interface{}, error) {
 	if pit == nil {
 		return nil, nil
 	}
-	return map[string]interface{}{
-		"id":         pit.Id,
-		"keep_alive": pit.KeepAlive,
-	}, nil
+	source := map[string]interface{}{
+		"id": pit.Id,
+	}
+
+	if pit.KeepAlive != "" {
+		source["keep_alive"] = pit.KeepAlive
+	}
+
+	return source, nil
 }