diff --git a/src/device/mouse_ps2.c b/src/device/mouse_ps2.c
index 35f0cd9e8..be8fd324f 100644
--- a/src/device/mouse_ps2.c
+++ b/src/device/mouse_ps2.c
@@ -96,6 +96,7 @@ ps2_report_coordinates(atkbc_dev_t *dev, int main)
     kbc_at_dev_queue_add(dev, buff[1], main);
     kbc_at_dev_queue_add(dev, buff[2], main);
     if (dev->flags & FLAG_INTMODE) {
+        delta_z = -delta_z;
         delta_z &= 0x0f;
 
         if (dev->flags & FLAG_5BTN) {