diff --git a/tests/mode_system_wiring_acceptance.rs b/tests/mode_system_wiring_acceptance.rs
index 256da9b..bd79b4e 100644
--- a/tests/mode_system_wiring_acceptance.rs
+++ b/tests/mode_system_wiring_acceptance.rs
@@ -25,7 +25,8 @@ struct Client {
 }
 
 const ROWS: u32 = 30;
-const COLS: u32 = 160;
+// Each split must leave room for a macOS temp path plus the mode segment.
+const COLS: u32 = 320;
 
 struct Grid {
     cells: Vec<Cell>,