diff --git a/crates/gc-formats/src/texture.rs b/crates/gc-formats/src/texture.rs
index a8c45c8..a321b99 100644
--- a/crates/gc-formats/src/texture.rs
+++ b/crates/gc-formats/src/texture.rs
@@ -273,12 +273,18 @@ mod tests {
     }
 
     #[test]
-    fn alpha_is_scaled_from_eight_bit_halves() {
+    fn alpha_runs_zero_to_0x80_and_scales_to_0xff() {
         assert_eq!(scale_alpha(0), 0);
         assert_eq!(scale_alpha(0x40), 0x80);
-        assert_eq!(scale_alpha(0x7f), 0xfe);
+        // 0x7F is 127/128, which is 253 and not 0xFE. This test was called
+        // `alpha_is_scaled_from_eight_bit_halves` and asserted 0xfe, pinning the
+        // `a * 2` implementation -- it had the bug in its name as well as its
+        // assertion. The rule is /128 * 255, not a doubling.
+        assert_eq!(scale_alpha(0x7f), 0xfd);
         assert_eq!(scale_alpha(0x80), 0xff);
         assert_eq!(scale_alpha(0xff), 0xff);
+        // A doubling cannot produce this, and the disc contains it.
+        assert_eq!(scale_alpha(0x7e), 0xfb);
     }
 
     /// A 2x1 image whose two texels select distinct CLUT entries.