diff --git a/internal/filechannel/filechannel.go b/internal/filechannel/filechannel.go
index a7ef201..ce1877e 100644
--- a/internal/filechannel/filechannel.go
+++ b/internal/filechannel/filechannel.go
@@ -43,6 +43,10 @@ import (
 	"github.com/risingwavelabs/filechannel/internal/utils"
 )
 
+// The flag to control the debug output. Debug outputs should print the non-critical messages. All
+// unexpected error messages must be printed without this flag.
+var verbose, _ = strconv.ParseBool(os.Getenv("DEBUG"))
+
 var (
 	ErrChecksumMismatch   = errors.New("channel corrupted: checksum mismatch")
 	ErrChannelClosed      = errors.New("channel closed")
@@ -1124,8 +1128,13 @@ func (fc *FileChannel) compress(ctx context.Context, index uint32) error {
 	default:
 	}
 
+	// Pin the segment. If failed, it means the watermark has moved forward and beyond the segment index.
+	// So we can just return immediately.
 	if !fc.segmentManager.Pin(index) {
-		return fmt.Errorf("failed to pin segment index %d", index)
+		if verbose {
+			_, _ = fmt.Fprintf(os.Stderr, "failed to pin segment index %d\n", index)
+		}
+		return nil
 	}
 	defer fc.segmentManager.Unpin(index)
 
@@ -1210,8 +1219,10 @@ func (fc *FileChannel) flushAndNotifyLoop(ctx context.Context) {
 		case <-ctx.Done():
 			return
 		case <-time.After(fc.flushInterval):
-			// FIXME: log the error
-			_ = fc.flushAndNotifyWithLock()
+			err := fc.flushAndNotifyWithLock()
+			if err != nil {
+				_, _ = fmt.Fprintf(os.Stderr, "failed to flush: %v\n", err)
+			}
 		}
 	}
 }