diff --git a/share/man/man4/wsp.4 b/share/man/man4/wsp.4
--- a/share/man/man4/wsp.4
+++ b/share/man/man4/wsp.4
@@ -66,6 +66,11 @@
 Tap to left-click can be controlled using the sysctl tunable
 .Nm hw.usb.wsp.enable_single_tap_clicks ,
 set to 0 to disable single tap clicks or 1 to enable them (default).
+Z-Axis sensitivity can be controlled using the sysctl tunable
+.Nm hw.usb.wsp.z_factor .
+Z-Axis inversion can be controlled using the sysctl tunable
+.Nm hw.usb.wsp.z_invert ,
+set to 0 to disable (default) or 1 to enable inversion.
 .Sh FILES
 .Nm
 creates a blocking pseudo-device file,
diff --git a/sys/dev/usb/input/wsp.c b/sys/dev/usb/input/wsp.c
--- a/sys/dev/usb/input/wsp.c
+++ b/sys/dev/usb/input/wsp.c
@@ -85,6 +85,7 @@
 static struct wsp_tuning {
 	int	scale_factor;
 	int	z_factor;
+	int	z_invert;
 	int	pressure_touch_threshold;
 	int	pressure_untouch_threshold;
 	int	pressure_tap_threshold;
@@ -95,6 +96,7 @@
 {
 	.scale_factor = 12,
 	.z_factor = 5,
+	.z_invert = 0,
 	.pressure_touch_threshold = 50,
 	.pressure_untouch_threshold = 10,
 	.pressure_tap_threshold = 120,
@@ -107,6 +109,7 @@
 {
 	WSP_CLAMP(ptun->scale_factor, 1, 63);
 	WSP_CLAMP(ptun->z_factor, 1, 63);
+	WSP_CLAMP(ptun->z_invert, 0, 1);
 	WSP_CLAMP(ptun->pressure_touch_threshold, 1, 255);
 	WSP_CLAMP(ptun->pressure_untouch_threshold, 1, 255);
 	WSP_CLAMP(ptun->pressure_tap_threshold, 1, 255);
@@ -118,6 +121,8 @@
     &wsp_tuning.scale_factor, 0, "movement scale factor");
 SYSCTL_INT(_hw_usb_wsp, OID_AUTO, z_factor, CTLFLAG_RWTUN,
     &wsp_tuning.z_factor, 0, "Z-axis scale factor");
+SYSCTL_INT(_hw_usb_wsp, OID_AUTO, z_invert, CTLFLAG_RWTUN,
+    &wsp_tuning.z_invert, 0, "enable Z-axis inversion");
 SYSCTL_INT(_hw_usb_wsp, OID_AUTO, pressure_touch_threshold, CTLFLAG_RWTUN,
     &wsp_tuning.pressure_touch_threshold, 0, "touch pressure threshold");
 SYSCTL_INT(_hw_usb_wsp, OID_AUTO, pressure_untouch_threshold, CTLFLAG_RWTUN,
@@ -1124,7 +1129,7 @@
 
 				dx = dy = 0;
 				if (sc->dz_count == 0)
-					dz = sc->dz_sum / tun.z_factor;
+					dz = (sc->dz_sum / tun.z_factor) * (tun.z_invert ? -1 : 1);
 				if (sc->scr_mode == WSP_SCR_HOR || 
 				    abs(sc->pos_x[0] - sc->pos_x[1]) > MAX_DISTANCE ||
 				    abs(sc->pos_y[0] - sc->pos_y[1]) > MAX_DISTANCE)