diff --git a/src/map.cpp b/src/map.cpp
index 0e2d34b..a8da898 100644
--- a/src/map.cpp
+++ b/src/map.cpp
@@ -29,7 +29,7 @@ void Map::block(uint8_t x, uint8_t y, Block *b) {
 
 Block *Map::block_under(Event *e) {
 	if (!e) { return NULL; }
-	uint16_t bx = e->event_x() / 2, by = e->event_y() / 2;
+	int16_t bx = e->event_x() / 2, by = e->event_y() / 2;
 	return bx >= 0 && by >= 0 && bx < _width && by < _height ? block((uint8_t)bx, (uint8_t)by) : NULL;
 }