diff --git a/weed/worker/tasks/erasure_coding/ec_task.go b/weed/worker/tasks/erasure_coding/ec_task.go
index e2e130f1b..6b0b35534 100644
--- a/weed/worker/tasks/erasure_coding/ec_task.go
+++ b/weed/worker/tasks/erasure_coding/ec_task.go
@@ -34,11 +34,12 @@ type ErasureCodingTask struct {
 	grpcDialOption grpc.DialOption
 
 	// EC parameters
-	dataShards      int32
-	parityShards    int32
-	targets         []*worker_pb.TaskTarget // Unified targets for EC shards
-	sources         []*worker_pb.TaskSource // Unified sources for cleanup
-	shardAssignment map[string][]string     // destination -> assigned shard types
+	dataShards        int32
+	parityShards      int32
+	targets           []*worker_pb.TaskTarget // Unified targets for EC shards
+	sources           []*worker_pb.TaskSource // Unified sources for cleanup
+	shardAssignment   map[string][]string     // destination -> assigned shard types
+	allowSourceDelete bool
 }
 
 // NewErasureCodingTask creates a new unified EC task instance
@@ -179,6 +180,7 @@ func (t *ErasureCodingTask) Execute(ctx context.Context, params *worker_pb.TaskP
 	if err := t.mountEcShards(); err != nil {
 		return fmt.Errorf("failed to mount EC shards: %v", err)
 	}
+	t.allowSourceDelete = true
 
 	// Step 6: Delete original volume
 	t.ReportProgressWithStage(90.0, "Deleting original volume")
@@ -469,6 +471,10 @@ func (t *ErasureCodingTask) mountEcShards() error {
 
 // deleteOriginalVolume deletes the original volume and all its replicas from all servers
 func (t *ErasureCodingTask) deleteOriginalVolume() error {
+	if !t.allowSourceDelete {
+		return fmt.Errorf("source deletion disabled: EC shards not fully distributed and mounted")
+	}
+
 	// Get replicas from task parameters (set during detection)
 	replicas := t.getReplicas()