diff --git a/debugger/commands.go b/debugger/commands.go
index 8e274db6..17778caf 100644
--- a/debugger/commands.go
+++ b/debugger/commands.go
@@ -122,7 +122,7 @@ var commandTemplate = input.CommandTemplate{
 	KeywordMissile:       "",
 	KeywordBall:          "",
 	KeywordPlayfield:     "",
-	KeywordDisplay:       "[|OFF]",
+	KeywordDisplay:       "[|OFF|OVERSCAN]",
 	KeywordMouse:         "[|X|Y]",
 	KeywordScript:        "%F",
 	KeywordDisassemble:   "",
@@ -560,17 +560,20 @@ func (dbg *Debugger) parseCommand(userInput string) (bool, error) {
 
 	case KeywordDisplay:
 		visibility := true
+		showOverscan := false
 		action, present := tokens.Get()
 		if present {
 			action = strings.ToUpper(action)
 			switch action {
 			case "OFF":
 				visibility = false
+			case "OVERSCAN":
+				showOverscan = true
 			default:
 				return false, fmt.Errorf("unknown display action (%s)", action)
 			}
 		}
-		err := dbg.vcs.TV.SetVisibility(visibility)
+		err := dbg.vcs.TV.SetVisibility(visibility, showOverscan)
 		if err != nil {
 			return false, err
 		}
diff --git a/gopher2600.go b/gopher2600.go
index 58f176c0..7561c5b3 100644
--- a/gopher2600.go
+++ b/gopher2600.go
@@ -117,7 +117,7 @@ func fps(cartridgeFile string, justTheVCS bool) error {
 			return fmt.Errorf("error preparing television: %s", err)
 		}
 	}
-	tv.SetVisibility(true)
+	tv.SetVisibility(true, false)
 
 	vcs, err := hardware.NewVCS(tv)
 	if err != nil {
@@ -162,7 +162,7 @@ func run(cartridgeFile string) error {
 	if err != nil {
 		return fmt.Errorf("error preparing television: %s", err)
 	}
-	tv.SetVisibility(true)
+	tv.SetVisibility(true, false)
 
 	vcs, err := hardware.NewVCS(tv)
 	if err != nil {
diff --git a/television/headless.go b/television/headless.go
index 2137f9d8..da1d662a 100644
--- a/television/headless.go
+++ b/television/headless.go
@@ -207,7 +207,7 @@ func (tv *HeadlessTV) Signal(attr SignalAttributes) {
 }
 
 // SetVisibility does nothing for the HeadlessTV
-func (tv *HeadlessTV) SetVisibility(visible bool) error {
+func (tv *HeadlessTV) SetVisibility(visible, showOverscan bool) error {
 	return nil
 }
 
diff --git a/television/sdltv/guiloop.go b/television/sdltv/guiloop.go
index da8fbb74..b1f0f73b 100644
--- a/television/sdltv/guiloop.go
+++ b/television/sdltv/guiloop.go
@@ -14,7 +14,7 @@ func (tv *SDLTV) guiLoop() {
 		// close window
 		case *sdl.QuitEvent:
 			// SetVisibility is outside of the critical section
-			tv.SetVisibility(false)
+			tv.SetVisibility(false, false)
 
 			// *CRITICAL SECTION*
 			// (R) tv.onWindowClose
@@ -26,17 +26,15 @@ func (tv *SDLTV) guiLoop() {
 			if ev.Type == sdl.KEYDOWN {
 				switch ev.Keysym.Sym {
 				case sdl.K_BACKQUOTE:
+					var showOverscan bool
+
 					// *CRITICAL SECTION*
-					// (W) tv.scr
-					// (R) tv.playScr, tv.dbgScr
+					// (R) tv.scr, tv.dbgScr
 					tv.guiLoopLock.Lock()
-					if tv.scr == tv.dbgScr {
-						tv.scr = tv.playScr
-					} else {
-						tv.scr = tv.dbgScr
-					}
-					tv.setWindowSize(tv.scr.width, tv.scr.height)
+					showOverscan = tv.scr != tv.dbgScr
 					tv.guiLoopLock.Unlock()
+
+					tv.SetVisibility(true, showOverscan)
 				}
 			}
 
diff --git a/television/sdltv/tvinterface.go b/television/sdltv/tvinterface.go
index a6ec6652..fcd9dbab 100644
--- a/television/sdltv/tvinterface.go
+++ b/television/sdltv/tvinterface.go
@@ -34,10 +34,20 @@ func (tv *SDLTV) Signal(attr television.SignalAttributes) {
 }
 
 // SetVisibility toggles the visiblity of the SDLTV window
-func (tv *SDLTV) SetVisibility(visible bool) error {
-	// *NON-CRITICAL SECTION* called from guiLoop but SDL handles its own
-	// concurrency conflicts
+func (tv *SDLTV) SetVisibility(visible, showOverscan bool) error {
+	// *CRITICAL SECTION*
+	// (W) tv.scr
+	// (R) tv.playScr, tv.dbgScr
+	tv.guiLoopLock.Lock()
+	if showOverscan {
+		tv.scr = tv.dbgScr
+	} else {
+		tv.scr = tv.playScr
+	}
+	tv.setWindowSize(tv.scr.width, tv.scr.height)
+	tv.guiLoopLock.Unlock()
 
+	// *NON-CRITICAL SECTION* SDL handles its own concurrency conflicts
 	if visible {
 		tv.window.Show()
 	} else {
diff --git a/television/television.go b/television/television.go
index d281eebc..e7617b28 100644
--- a/television/television.go
+++ b/television/television.go
@@ -43,7 +43,7 @@ type Television interface {
 	MachineInfoTerse() string
 	MachineInfo() string
 	Signal(SignalAttributes)
-	SetVisibility(visible bool) error
+	SetVisibility(visible, showOverscan bool) error
 	SetPause(pause bool) error
 
 	RequestTVState(TVStateReq) (*TVState, error)
@@ -74,7 +74,7 @@ func (tv DummyTV) String() string {
 func (DummyTV) Signal(SignalAttributes) {}
 
 // SetVisibility (with dummyTV reciever) is the null implementation
-func (DummyTV) SetVisibility(visible bool) error {
+func (DummyTV) SetVisibility(visible, showOverscan bool) error {
 	return nil
 }