diff --git a/tests/files/palette_should_be_grayscale.png b/tests/files/palette_should_be_grayscale.png
index d3b50e0e..dc820aea 100644
Binary files a/tests/files/palette_should_be_grayscale.png and b/tests/files/palette_should_be_grayscale.png differ
diff --git a/tests/oxipng.rs b/tests/oxipng.rs
index 87c1c9d5..4c575bab 100644
--- a/tests/oxipng.rs
+++ b/tests/oxipng.rs
@@ -358,7 +358,7 @@ fn palette_should_be_grayscale() {
     };
 
     assert!(png.ihdr_data.color_type == png::ColorType::Grayscale);
-    assert!(png.ihdr_data.bit_depth == png::BitDepth::Four);
+    assert!(png.ihdr_data.bit_depth == png::BitDepth::Eight);
 
     let old_png = image::open(&input).unwrap();
     let new_png = image::open(&output).unwrap();