diff --git a/src/video/allegro_v.cpp b/src/video/allegro_v.cpp
index 7f831e0da4..faf4091151 100644
--- a/src/video/allegro_v.cpp
+++ b/src/video/allegro_v.cpp
@@ -40,14 +40,13 @@ static FVideoDriver_Allegro iFVideoDriver_Allegro;
 
 static BITMAP *_allegro_screen;
 
-#define MAX_DIRTY_RECTS 100
-static PointDimension _dirty_rects[MAX_DIRTY_RECTS];
-static int _num_dirty_rects;
+static PointDimension _dirty_rects[100];
+static size_t _num_dirty_rects;
 static Palette _local_palette; ///< Current palette to use for drawing.
 
 void VideoDriver_Allegro::MakeDirty(int left, int top, int width, int height)
 {
-	if (_num_dirty_rects < MAX_DIRTY_RECTS) {
+	if (_num_dirty_rects < std::size(_dirty_rects)) {
 		_dirty_rects[_num_dirty_rects].x = left;
 		_dirty_rects[_num_dirty_rects].y = top;
 		_dirty_rects[_num_dirty_rects].width = width;
@@ -60,16 +59,16 @@ void VideoDriver_Allegro::Paint()
 {
 	PerformanceMeasurer framerate(PFE_VIDEO);
 
-	int n = _num_dirty_rects;
+	size_t n = _num_dirty_rects;
 	if (n == 0) return;
 
 	_num_dirty_rects = 0;
-	if (n > MAX_DIRTY_RECTS) {
+	if (n > std::size(_dirty_rects)) {
 		blit(_allegro_screen, screen, 0, 0, 0, 0, _allegro_screen->w, _allegro_screen->h);
 		return;
 	}
 
-	for (int i = 0; i < n; i++) {
+	for (size_t i = 0; i < n; i++) {
 		blit(_allegro_screen, screen, _dirty_rects[i].x, _dirty_rects[i].y, _dirty_rects[i].x, _dirty_rects[i].y, _dirty_rects[i].width, _dirty_rects[i].height);
 	}
 }