diff --git a/engines/mortevielle/graphics.cpp b/engines/mortevielle/graphics.cpp
index 27595992c77..ee9c63228be 100644
--- a/engines/mortevielle/graphics.cpp
+++ b/engines/mortevielle/graphics.cpp
@@ -1011,6 +1011,7 @@ void ScreenSurface::clearScreen() {
  *		simulate the original 640x400 surface, all Y values have to be doubled
  */
 void ScreenSurface::setPixel(const Common::Point &pt, int palIndex) {
+	assert((pt.x >= 0) && (pt.y >= 0) && (pt.x <= SCREEN_WIDTH) && (pt.y <= SCREEN_ORIG_HEIGHT));
 	Graphics::Surface destSurface = lockArea(Common::Rect(pt.x, pt.y * 2, pt.x + 1, (pt.y + 1) * 2));
 
 	byte *destP = (byte *)destSurface.pixels;
diff --git a/engines/mortevielle/mortevielle.h b/engines/mortevielle/mortevielle.h
index 3010ae8664b..0555f302abe 100644
--- a/engines/mortevielle/mortevielle.h
+++ b/engines/mortevielle/mortevielle.h
@@ -42,6 +42,7 @@ enum {
 
 #define SCREEN_WIDTH 640
 #define SCREEN_HEIGHT 400
+#define SCREEN_ORIG_HEIGHT 200
 #define MORT_DAT_REQUIRED_VERSION 1
 #define MORT_DAT "mort.dat"
 #define GAME_FRAME_DELAY (1000 / 50)
diff --git a/engines/mortevielle/mouse.cpp b/engines/mortevielle/mouse.cpp
index 2ea8434a1cd..04b6c116e0d 100644
--- a/engines/mortevielle/mouse.cpp
+++ b/engines/mortevielle/mouse.cpp
@@ -265,8 +265,6 @@ void show_mouse() {
 }
 
 void pos_mouse(int x, int y) {
-	registres reg;
-
 	if (x > 314 * res)  x = 314 * res;
 	else if (x < 0)  x = 0;
 	if (y > 199)  y = 199;
@@ -286,7 +284,7 @@ void read_pos_mouse(int &x, int &y, int &c) {
 void mov_mouse(bool &funct, char &key) {
 	bool p_key;
 	char in1, in2;
-	int x, y, cx, cy, cd;
+	int cx, cy, cd;
 
 	// If mouse button clicked, return it
 	if (g_vm->getMouseButtons() != 0) {