diff --git a/platforms/opencv/camera_driver_test.go b/platforms/opencv/camera_driver_test.go
index 097c69c9..65286408 100644
--- a/platforms/opencv/camera_driver_test.go
+++ b/platforms/opencv/camera_driver_test.go
@@ -28,7 +28,7 @@ func TestCameraDriver(t *testing.T) {
 func TestCameraDriverStart(t *testing.T) {
 	sem := make(chan bool)
 	d := initTestCameraDriver()
-	gobottest.Assert(t, len(d.Start()), 0)
+	gobottest.Assert(t, d.Start(), nil)
 	d.On(d.Event("frame"), func(data interface{}) {
 		sem <- true
 	})
@@ -39,13 +39,13 @@ func TestCameraDriverStart(t *testing.T) {
 	}
 
 	d = NewCameraDriver("")
-	gobottest.Assert(t, len(d.Start()), 0)
+	gobottest.Assert(t, d.Start(), nil)
 
 	d = NewCameraDriver(true)
-	gobottest.Refute(t, len(d.Start()), 0)
+	gobottest.Refute(t, d.Start(), nil)
 }
 
 func TestCameraDriverHalt(t *testing.T) {
 	d := initTestCameraDriver()
-	gobottest.Assert(t, len(d.Halt()), 0)
+	gobottest.Assert(t, d.Halt(), nil)
 }
diff --git a/platforms/opencv/window_driver.go b/platforms/opencv/window_driver.go
index 97a713dd..6be51fd4 100644
--- a/platforms/opencv/window_driver.go
+++ b/platforms/opencv/window_driver.go
@@ -31,14 +31,14 @@ func (w *WindowDriver) SetName(n string)             { w.name = n }
 func (w *WindowDriver) Connection() gobot.Connection { return nil }
 
 // Start starts window thread and driver
-func (w *WindowDriver) Start() (errs []error) {
+func (w *WindowDriver) Start() (err error) {
 	cv.StartWindowThread()
 	w.start(w)
 	return
 }
 
 // Halt returns true if camera is halted successfully
-func (w *WindowDriver) Halt() (errs []error) { return }
+func (w *WindowDriver) Halt() (err error) { return }
 
 // ShowImage displays image in window
 func (w *WindowDriver) ShowImage(image *cv.IplImage) {
diff --git a/platforms/opencv/window_driver_test.go b/platforms/opencv/window_driver_test.go
index 3beae5c1..bf2531a7 100644
--- a/platforms/opencv/window_driver_test.go
+++ b/platforms/opencv/window_driver_test.go
@@ -25,12 +25,12 @@ func TestWindowDriver(t *testing.T) {
 
 func TestWindowDriverStart(t *testing.T) {
 	d := initTestWindowDriver()
-	gobottest.Assert(t, len(d.Start()), 0)
+	gobottest.Assert(t, d.Start(), nil)
 }
 
 func TestWindowDriverHalt(t *testing.T) {
 	d := initTestWindowDriver()
-	gobottest.Assert(t, len(d.Halt()), 0)
+	gobottest.Assert(t, d.Halt(), nil)
 }
 
 func TestWindowDriverShowImage(t *testing.T) {