diff --git a/debugger/debugger.go b/debugger/debugger.go
index 8df44c20..8aa92ed3 100644
--- a/debugger/debugger.go
+++ b/debugger/debugger.go
@@ -149,7 +149,7 @@ func NewDebugger() (*Debugger, error) {
 	dbg.gui.SetFeature(gui.ReqSetAllowDebugging, true)
 
 	// create a new VCS instance
-	dbg.vcs, err = hardware.NewVCS(btv)
+	dbg.vcs, err = hardware.NewVCS(dbg.gui)
 	if err != nil {
 		return nil, errors.NewFormattedError(errors.DebuggerError, err)
 	}
diff --git a/errors/messages.go b/errors/messages.go
index 5e32075a..93fd5f6e 100644
--- a/errors/messages.go
+++ b/errors/messages.go
@@ -71,12 +71,12 @@ var messages = map[Errno]string{
 	UnknownPeriphEvent:        "periperal error: %s: unsupported event (%v)",
 
 	// tv
-	UnknownTVRequest: "tv error: unsupported tv request (%v)",
+	UnknownTVRequest: "tv error: unsupported request (%v)",
 	BasicTelevision:  "tv error: BasicTelevision: %s",
 	ImageTV:          "tv error: ImageTV: %s",
 	DigestTV:         "tv error: DigestTV: %s",
 
 	// gui
-	UnknownGUIRequest: "gui error: unsupported gui request (%v)",
+	UnknownGUIRequest: "gui error: unsupported request (%v)",
 	SDL:               "gui error: SDL: %s",
 }
diff --git a/television/basic.go b/television/basic.go
index a000c2bb..95f3350b 100644
--- a/television/basic.go
+++ b/television/basic.go
@@ -216,7 +216,7 @@ func (btv *BasicTelevision) Signal(sig SignalAttributes) error {
 
 	// push screen limits outwards as required
 	if !sig.VBlank {
-		if btv.endOfScreen && btv.scanline > btv.pendingVisibleBottom {
+		if !btv.endOfScreen && btv.scanline > btv.pendingVisibleBottom {
 			btv.pendingVisibleBottom = btv.scanline + 2
 
 			// keep within limits