diff --git a/pkg/config/item.go b/pkg/config/item.go
index a7f59eb..5712cf8 100644
--- a/pkg/config/item.go
+++ b/pkg/config/item.go
@@ -1,6 +1,9 @@
 package config
 
-import "github.com/suzuki-shunsuke/buildflow/pkg/expr"
+import (
+	"github.com/suzuki-shunsuke/buildflow/pkg/expr"
+	"github.com/suzuki-shunsuke/go-convmap/convmap"
+)
 
 type Items struct {
 	Items   interface{}
@@ -19,3 +22,29 @@ func (items Items) Run(params map[string]interface{}) (interface{}, error) {
 	}
 	return a, nil
 }
+
+func (items *Items) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var src interface{}
+	if err := unmarshal(&src); err != nil {
+		return err
+	}
+	switch t := src.(type) {
+	case string:
+		prog, err := expr.New(t)
+		if err != nil {
+			return err
+		}
+		items.Program = prog
+		return nil
+	default:
+		if t == nil {
+			return nil
+		}
+		a, err := convmap.Convert(t)
+		if err != nil {
+			return err
+		}
+		items.Items = a
+		return nil
+	}
+}
diff --git a/pkg/config/task.go b/pkg/config/task.go
index 4f548f6..5d59635 100644
--- a/pkg/config/task.go
+++ b/pkg/config/task.go
@@ -5,30 +5,27 @@ import (
 
 	"github.com/suzuki-shunsuke/buildflow/pkg/constant"
 	"github.com/suzuki-shunsuke/buildflow/pkg/execute"
-	"github.com/suzuki-shunsuke/buildflow/pkg/expr"
-	"github.com/suzuki-shunsuke/go-convmap/convmap"
 )
 
 type Task struct {
-	Name          Template
-	Type          string `yaml:"-"`
-	When          Bool
-	WhenFile      string `yaml:"when_file"`
-	Dependency    Dependency
-	Command       Command
-	ReadFile      ReadFile  `yaml:"read_file"`
-	WriteFile     WriteFile `yaml:"write_file"`
-	HTTP          HTTP
-	Timeout       execute.Timeout
-	Items         interface{}
-	Item          Item `yaml:"-"`
-	CompiledItems Items
-	Meta          map[string]interface{}
-	Output        Script
-	Input         Script
-	InputFile     string `yaml:"input_file"`
-	OutputFile    string `yaml:"output_file"`
-	Import        string
+	Name       Template
+	Type       string `yaml:"-"`
+	When       Bool
+	WhenFile   string `yaml:"when_file"`
+	Dependency Dependency
+	Command    Command
+	ReadFile   ReadFile  `yaml:"read_file"`
+	WriteFile  WriteFile `yaml:"write_file"`
+	HTTP       HTTP
+	Timeout    execute.Timeout
+	Items      Items
+	Item       Item `yaml:"-"`
+	Meta       map[string]interface{}
+	Output     Script
+	Input      Script
+	InputFile  string `yaml:"input_file"`
+	OutputFile string `yaml:"output_file"`
+	Import     string
 }
 
 type WriteFile struct {
@@ -42,22 +39,6 @@ func (task *Task) Set() error {
 		return err
 	}
 
-	if s, ok := task.Items.(string); ok {
-		prog, err := expr.New(s)
-		if err != nil {
-			return err
-		}
-		task.CompiledItems = Items{
-			Program: prog,
-		}
-	} else if task.Items != nil {
-		a, err := convmap.Convert(task.Items)
-		if err != nil {
-			return err
-		}
-		task.Items = a
-	}
-
 	if err := convertMeta(task.Meta); err != nil {
 		return err
 	}
diff --git a/pkg/controller/expand.go b/pkg/controller/expand.go
index ebe318d..a0b94dc 100644
--- a/pkg/controller/expand.go
+++ b/pkg/controller/expand.go
@@ -73,7 +73,14 @@ func expandItems(task config.Task, items interface{}, templateParams Params) ([]
 }
 
 func Expand(task config.Task, params Params) ([]config.Task, error) {
-	if task.Items == nil {
+	if task.Items.Items != nil {
+		return expandItems(task, task.Items.Items, params)
+	}
+	items, err := task.Items.Run(params.ToExpr())
+	if err != nil {
+		return nil, err
+	}
+	if items == nil {
 		name, err := task.Name.New(params.ToTemplate())
 		if err != nil {
 			return nil, err
@@ -82,12 +89,5 @@ func Expand(task config.Task, params Params) ([]config.Task, error) {
 		t.Name = name
 		return []config.Task{t}, nil
 	}
-	if _, ok := task.Items.(string); ok {
-		items, err := task.CompiledItems.Run(params.ToExpr())
-		if err != nil {
-			return nil, err
-		}
-		return expandItems(task, items, params)
-	}
-	return expandItems(task, task.Items, params)
+	return expandItems(task, items, params)
 }