diff --git a/crates/gpu/src/shaders/fx_pixel2.wgsl b/crates/gpu/src/shaders/fx_pixel2.wgsl
index 21bb8b5d8..a01567540 100644
--- a/crates/gpu/src/shaders/fx_pixel2.wgsl
+++ b/crates/gpu/src/shaders/fx_pixel2.wgsl
@@ -647,7 +647,9 @@ fn fp2_hextile(@builtin(global_invocation_id) gid: vec3<u32>) {
     // stylize3::hex_cell (cube rounding).
     let q = (0.5773502691896257 * u - v / 3.0) / r;
     let rr = (2.0 / 3.0 * v) / r;
-    let ccy = -q - rr;
+    // Evaluate the third cube coordinate symmetrically with q so the centerline
+    // tie is not broken by subtracting separately rounded coordinates.
+    let ccy = (-0.5773502691896257 * u - v / 3.0) / r;
     var rx = round_away(q);
     let ry = round_away(ccy);
     var rz = round_away(rr);
diff --git a/crates/script/src/tests_services.rs b/crates/script/src/tests_services.rs
index c0ecfab40..eaabd2902 100644
--- a/crates/script/src/tests_services.rs
+++ b/crates/script/src/tests_services.rs
@@ -11,6 +11,8 @@ use crate::run_code;
 #[derive(Default)]
 struct Mem(Mutex<HashMap<String, Vec<u8>>>);
 
+// A poisoned fixture mutex should fail the test.
+#[allow(clippy::unwrap_used)]
 impl Services for Mem {
     fn read_file(&self, path: &str) -> std::io::Result<Vec<u8>> {
         self.0.lock().unwrap().get(path).cloned().ok_or_else(|| std::io::Error::new(std::io::ErrorKind::NotFound, path.to_string()))