diff --git a/background.go b/background.go
index fb860ce..316f527 100644
--- a/background.go
+++ b/background.go
@@ -37,14 +37,11 @@ type Background struct {
 
 // Config specifies the background-task processing behavior.
 type Config struct {
-	// Max number of concurrent workers to process tasks.
+	// Maximum number of concurrent workers to process tasks.
 	//
 	// If set to zero or negative value, NewBackground will overwrite the value to one.
 	Concurrency int
 
-	// TODO(hibiken): Add ShutdownTimeout
-	// ShutdownTimeout time.Duration
-
 	// Function to calculate retry delay for a failed task.
 	//
 	// By default, it uses exponential backoff algorithm to calculate the delay.
diff --git a/processor.go b/processor.go
index 1aafc93..39d82b3 100644
--- a/processor.go
+++ b/processor.go
@@ -70,7 +70,7 @@ func (p *processor) stop() {
 func (p *processor) terminate() {
 	p.stop()
 
-	// TODO(hibiken): Allow user to customize this timeout value.
+	// IDEA: Allow user to customize this timeout value.
 	const timeout = 8 * time.Second
 	time.AfterFunc(timeout, func() { close(p.quit) })
 	log.Println("[INFO] Waiting for all workers to finish...")