diff --git a/internal/proxy/task.go b/internal/proxy/task.go
index 27d300f485..45c399c6c4 100644
--- a/internal/proxy/task.go
+++ b/internal/proxy/task.go
@@ -3165,7 +3165,7 @@ func getPrimaryKeysFromExpr(schema *schemapb.CollectionSchema, expr string) (res
 	// delete request only support expr "id in [a, b]"
 	termExpr, ok := plan.Node.(*planpb.PlanNode_Predicates).Predicates.Expr.(*planpb.Expr_TermExpr)
 	if !ok {
-		return res, 0, fmt.Errorf("invalid plan node type")
+		return res, 0, fmt.Errorf("invalid plan node type, only pk in [1, 2] supported")
 	}
 
 	res = &schemapb.IDs{}
diff --git a/internal/proxy/task_test.go b/internal/proxy/task_test.go
index 813eda76d1..6c154a38f0 100644
--- a/internal/proxy/task_test.go
+++ b/internal/proxy/task_test.go
@@ -1844,6 +1844,42 @@ func TestTask_Int64PrimaryKey(t *testing.T) {
 		assert.NoError(t, task.PreExecute(ctx))
 		assert.NoError(t, task.Execute(ctx))
 		assert.NoError(t, task.PostExecute(ctx))
+
+		task2 := &deleteTask{
+			Condition: NewTaskCondition(ctx),
+			BaseDeleteTask: msgstream.DeleteMsg{
+				BaseMsg: msgstream.BaseMsg{},
+				DeleteRequest: internalpb.DeleteRequest{
+					Base: &commonpb.MsgBase{
+						MsgType:   commonpb.MsgType_Delete,
+						MsgID:     0,
+						Timestamp: 0,
+						SourceID:  Params.ProxyCfg.GetNodeID(),
+					},
+					CollectionName: collectionName,
+					PartitionName:  partitionName,
+				},
+			},
+			deleteExpr: "int64 not in [0, 1]",
+			ctx:        ctx,
+			result: &milvuspb.MutationResult{
+				Status: &commonpb.Status{
+					ErrorCode: commonpb.ErrorCode_Success,
+					Reason:    "",
+				},
+				IDs:          nil,
+				SuccIndex:    nil,
+				ErrIndex:     nil,
+				Acknowledged: false,
+				InsertCnt:    0,
+				DeleteCnt:    0,
+				UpsertCnt:    0,
+				Timestamp:    0,
+			},
+			chMgr:    chMgr,
+			chTicker: ticker,
+		}
+		assert.Error(t, task2.PreExecute(ctx))
 	})
 }
 
@@ -2064,6 +2100,42 @@ func TestTask_VarCharPrimaryKey(t *testing.T) {
 		assert.NoError(t, task.PreExecute(ctx))
 		assert.NoError(t, task.Execute(ctx))
 		assert.NoError(t, task.PostExecute(ctx))
+
+		task2 := &deleteTask{
+			Condition: NewTaskCondition(ctx),
+			BaseDeleteTask: msgstream.DeleteMsg{
+				BaseMsg: msgstream.BaseMsg{},
+				DeleteRequest: internalpb.DeleteRequest{
+					Base: &commonpb.MsgBase{
+						MsgType:   commonpb.MsgType_Delete,
+						MsgID:     0,
+						Timestamp: 0,
+						SourceID:  Params.ProxyCfg.GetNodeID(),
+					},
+					CollectionName: collectionName,
+					PartitionName:  partitionName,
+				},
+			},
+			deleteExpr: "varChar not in [\"milvus\", \"test\"]",
+			ctx:        ctx,
+			result: &milvuspb.MutationResult{
+				Status: &commonpb.Status{
+					ErrorCode: commonpb.ErrorCode_Success,
+					Reason:    "",
+				},
+				IDs:          nil,
+				SuccIndex:    nil,
+				ErrIndex:     nil,
+				Acknowledged: false,
+				InsertCnt:    0,
+				DeleteCnt:    0,
+				UpsertCnt:    0,
+				Timestamp:    0,
+			},
+			chMgr:    chMgr,
+			chTicker: ticker,
+		}
+		assert.Error(t, task2.PreExecute(ctx))
 	})
 }