diff --git a/drivers/input/misc/mma8450.c b/drivers/input/misc/mma8450.c
index 480557f..f330969 100644
--- a/drivers/input/misc/mma8450.c
+++ b/drivers/input/misc/mma8450.c
@@ -123,9 +123,9 @@
 	if (ret < 0)
 		return;
 
-	x = ((buf[1] << 4) & 0xff0) | (buf[0] & 0xf);
-	y = ((buf[3] << 4) & 0xff0) | (buf[2] & 0xf);
-	z = ((buf[5] << 4) & 0xff0) | (buf[4] & 0xf);
+	x = ((int)(s8)buf[1] << 4) | (buf[0] & 0xf);
+	y = ((int)(s8)buf[3] << 4) | (buf[2] & 0xf);
+	z = ((int)(s8)buf[5] << 4) | (buf[4] & 0xf);
 
 	input_report_abs(dev->input, ABS_X, x);
 	input_report_abs(dev->input, ABS_Y, y);