diff --git a/include/effect_matrix.h b/include/effect_matrix.h
index 9105525..8b75c30 100644
--- a/include/effect_matrix.h
+++ b/include/effect_matrix.h
@@ -9,7 +9,7 @@
 class MatrixEffectColumn {
 protected:
     Window* window;
-    accum88 x, y;
+    saccum78 x, y;
     uint8_t length = 1;
     uint8_t _direction = 2;
     bool _random_direction = false;
diff --git a/src/effect_matrix.cpp b/src/effect_matrix.cpp
index 33f8ff4..476f8f5 100644
--- a/src/effect_matrix.cpp
+++ b/src/effect_matrix.cpp
@@ -47,7 +47,7 @@ void MatrixEffectColumn::advance(uint16_t ms) {
 	switch(_direction) {
 		case DIR_NORTH:
 			y-=speed * ms;
-			if ((y>>8) > window->height && (y>>8) + length > window->height) running=false;
+			if ((y>>8) + length < 0) running=false;
 			break;
 		case DIR_EAST:
 			x+=speed * ms;
@@ -59,7 +59,7 @@ void MatrixEffectColumn::advance(uint16_t ms) {
 			break;
 		case DIR_WEST:
 			x-=speed * ms;
-			if ((x>>8) > window->width && (y>>8) + length > window->width) running=false;
+			if ((x>>8) + length < 0) running=false;
 			break;
 	}
 }