diff --git a/filter/mog.go b/filter/mog.go
index b83b039c..9519b656 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 0, fmt.Errorf("image can't be decoded: %w", err)
+		return len(f), fmt.Errorf("image can't be decoded: %w", err)
 	}
 	defer img.Close()
 
@@ -135,7 +135,7 @@ func (m *MOGFilter) Write(f []byte) (int, error) {
 
 	// Don't write to destination if there is no motion.
 	if len(contours) == 0 {
-		return 0, nil
+		return len(f), nil
 	}
 
 	// Write to destination, past 4 frames then current frame.
@@ -143,7 +143,7 @@ func (m *MOGFilter) Write(f []byte) (int, error) {
 		_, err := m.dst.Write(h)
 		m.hold[i] = nil
 		if err != nil {
-			return 0, err
+			return len(f), fmt.Errorf("could not write previous frames: %w", err)
 		}
 	}
 	return m.dst.Write(f)