diff --git a/src/device/mouse_ps2.c b/src/device/mouse_ps2.c
index c05753afb..35f0cd9e8 100644
--- a/src/device/mouse_ps2.c
+++ b/src/device/mouse_ps2.c
@@ -84,7 +84,7 @@ ps2_report_coordinates(atkbc_dev_t *dev, int main)
 
     mouse_subtract_coords(&delta_x, &delta_y, &overflow_x, &overflow_y,
                           -256, 255, 1, 0);
-    mouse_subtract_z(&delta_z, -8, 7, 0);
+    mouse_subtract_z(&delta_z, -8, 7, 1);
 
     buff[0] |= (overflow_y << 7) | (overflow_x << 6) |
               ((delta_y & 0x0100) >> 3) | ((delta_x & 0x0100) >> 4) |