diff --git a/src/filter.c b/src/filter.c
index 0bb066c..984046d 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -307,6 +307,15 @@ calculate_acceleration(struct pointer_accelerator *accel,
 
 	factor = factor / 6.0;
 
+	{
+		static uint64_t time_offset = 0;
+
+		if (time_offset == 0)
+			time_offset = time;
+
+		fprintf(stderr, "%d %f %f\n", us2ms(time - time_offset), velocity * 1000, factor);
+	}
+
 	return factor; /* unitless factor */
 }