diff --git a/models/workflow_execution/workflow_execution.go b/models/workflow_execution/workflow_execution.go
index a88a196..751ab18 100755
--- a/models/workflow_execution/workflow_execution.go
+++ b/models/workflow_execution/workflow_execution.go
@@ -191,6 +191,9 @@ func (d *WorkflowExecution) Book(executionsID string, wfID string, priceds map[t
 	booking = append(booking, d.bookEach(executionsID, wfID, tools.DATA_RESOURCE, priceds[tools.DATA_RESOURCE])...)
 	for _, p := range booking {
 		p.SetID(uuid.NewString())
+		if d.BookingsState == nil {
+			d.BookingsState = map[string]bool{}
+		}
 		d.BookingsState[p.GetID()] = false
 	}
 	return booking