diff --git a/src/grome/matrix.zig b/src/grome/matrix.zig
index d056eee..c66fcd9 100644
--- a/src/grome/matrix.zig
+++ b/src/grome/matrix.zig
@@ -172,7 +172,7 @@ pub fn SubMatrix(comptime T: type) type {
         }
 
         pub fn set(self: *@This(), loc: Point, val: T) !void {
-            if (loc.x >= self._mask.width or loc.y >= self._mask.width) {
+            if (loc.x >= self._mask.width or loc.y >= self._mask.height) {
                 return Error.OutOfBounds;
             }