diff --git a/src/evdev-mt-touchpad.c b/src/evdev-mt-touchpad.c
index e25997df..73ea8a8d 100644
--- a/src/evdev-mt-touchpad.c
+++ b/src/evdev-mt-touchpad.c
@@ -174,7 +174,7 @@ tp_estimate_delta(int x0, int x1, int x2, int x3)
 	return (x0 + x1 - x2 - x3) / 4;
 }
 
-static void
+void
 tp_get_delta(struct tp_touch *t, double *dx, double *dy)
 {
 	if (t->history.count < 4) {
diff --git a/src/evdev-mt-touchpad.h b/src/evdev-mt-touchpad.h
index d12647de..907aec83 100644
--- a/src/evdev-mt-touchpad.h
+++ b/src/evdev-mt-touchpad.h
@@ -102,4 +102,7 @@ struct tp_dispatch {
 #define tp_for_each_touch(_tp, _t) \
 	for (unsigned int _i = 0; _i < (_tp)->ntouches && (_t = &(_tp)->touches[_i]); _i++)
 
+void
+tp_get_delta(struct tp_touch *t, double *dx, double *dy);
+
 #endif