diff --git a/filter/mog.go b/filter/mog.go
index b86e1cdf..ca318140 100644
--- a/filter/mog.go
+++ b/filter/mog.go
@@ -87,7 +87,7 @@ func (m *MOGFilter) Write(f []byte) (int, error) {
 	m.hfCount = 0
 	img, err := gocv.IMDecode(f, gocv.IMReadColor)
 	if err != nil {
-		return len(f), fmt.Errorf("image can't be decoded: %w", err)
+		return 0, fmt.Errorf("image can't be decoded: %w", err)
 	}
 	defer img.Close()