diff --git a/src/video/ataricommon/SDL_xbiosevents.c b/src/video/ataricommon/SDL_xbiosevents.c
index b744252fc99882e8d477ef4b825fdbe13c010cec..5d1fa3c51d3296b753e6eb78da727bb404f5ca47 100644
--- a/src/video/ataricommon/SDL_xbiosevents.c
+++ b/src/video/ataricommon/SDL_xbiosevents.c
@@ -49,7 +49,8 @@ void SDL_AtariXbios_InstallVectors(int vectors_mask)
 	void *oldpile;
 
 	/* Clear variables */
-	SDL_AtariXbios_mouseb =
+	SDL_AtariXbios_mouselock =
+		SDL_AtariXbios_mouseb =
 		SDL_AtariXbios_mousex =
 		SDL_AtariXbios_mousey =
 		SDL_AtariXbios_joystick =
@@ -146,3 +147,8 @@ void SDL_AtariXbios_PostMouseEvents(_THIS, SDL_bool buttonEvents)
 		atari_prevmouseb = SDL_AtariXbios_mouseb;
 	}
 }
+
+void SDL_AtariXbios_LockMousePosition(SDL_bool lockPosition)
+{
+	SDL_AtariXbios_mouselock = lockPosition;
+}
diff --git a/src/video/ataricommon/SDL_xbiosevents_c.h b/src/video/ataricommon/SDL_xbiosevents_c.h
index 05761bde4f14ddbedc02b83b2bcb42b47a06801a..9f746fbbd977485fc0ddfbec24c1012b447906ad 100644
--- a/src/video/ataricommon/SDL_xbiosevents_c.h
+++ b/src/video/ataricommon/SDL_xbiosevents_c.h
@@ -43,5 +43,6 @@ extern int SDL_AtariXbios_enabled;
 extern void SDL_AtariXbios_InstallVectors(int vectors_mask);
 extern void SDL_AtariXbios_RestoreVectors(void);
 extern void SDL_AtariXbios_PostMouseEvents(_THIS, SDL_bool buttonEvents);
+extern void SDL_AtariXbios_LockMousePosition(SDL_bool lockPosition);
 
 #endif /* _SDL_XBIOSEVENTS_H_ */
diff --git a/src/video/ataricommon/SDL_xbiosinterrupt.S b/src/video/ataricommon/SDL_xbiosinterrupt.S
index 548561ca4bd1c9bc2c5dcf10e192bff146aefbaf..a76df37683bc1382cf41c27aca769ab935285c91 100644
--- a/src/video/ataricommon/SDL_xbiosinterrupt.S
+++ b/src/video/ataricommon/SDL_xbiosinterrupt.S
@@ -33,6 +33,7 @@
 	.globl	_SDL_AtariXbios_MouseVector
 	.globl	_SDL_AtariXbios_JoystickVector
 
+	.globl	_SDL_AtariXbios_mouselock
 	.globl	_SDL_AtariXbios_mouseb
 	.globl	_SDL_AtariXbios_mousex
 	.globl	_SDL_AtariXbios_mousey
@@ -125,6 +126,13 @@ _SDL_AtariXbios_MouseVector:
 	extw	d0
 	addw	d0,_SDL_AtariXbios_mousey
 
+	/* Lock mouse position ? */
+	tstw	_SDL_AtariXbios_mouselock
+	beq.s	no_mouse_lock
+	clrb	a0@(1)
+	clrb	a0@(2)
+no_mouse_lock:
+
 	/* Jump through old vector */
 	movel	sp@+,d0
 
@@ -133,10 +141,9 @@ _SDL_AtariXbios_MouseVector:
 
 	.data
 	.even
+	.comm	_SDL_AtariXbios_mouselock,2*1
 	.comm	_SDL_AtariXbios_mousex,2*1
-	.even
 	.comm	_SDL_AtariXbios_mousey,2*1
-	.even
 	.comm	_SDL_AtariXbios_mouseb,2*1
 
 /*--- Our joystick vector ---*/
diff --git a/src/video/ataricommon/SDL_xbiosinterrupt_s.h b/src/video/ataricommon/SDL_xbiosinterrupt_s.h
index cee4260b57eba2d2edcd9887eda4ee9ae63e3826..429c1705e3289a4ebea018cb5a049b2780ab4f9a 100644
--- a/src/video/ataricommon/SDL_xbiosinterrupt_s.h
+++ b/src/video/ataricommon/SDL_xbiosinterrupt_s.h
@@ -36,6 +36,7 @@
 
 /* Variables */
 
+extern volatile Uint16 SDL_AtariXbios_mouselock;	/* mouse lock position */
 extern volatile Uint16 SDL_AtariXbios_mouseb;	/* buttons */
 extern volatile Sint16 SDL_AtariXbios_mousex;	/* X relative motion */
 extern volatile Sint16 SDL_AtariXbios_mousey;	/* Y relative motion */