diff --git a/src/distance_transform.rs b/src/distance_transform.rs
index 3ceec38b..e151ee2f 100644
--- a/src/distance_transform.rs
+++ b/src/distance_transform.rs
@@ -484,13 +484,13 @@ mod tests {
     #[test]
     fn test_distance_transform_saturation() {
         // A single foreground pixel in the top-left
-        let image = GrayImage::from_fn(300, 300, |x, y| match (x, y) {
+        let image = GrayImage::from_fn(300, 3, |x, y| match (x, y) {
             (0, 0) => Luma([255u8]),
             _ => Luma([0u8]),
         });
 
         // Distances should not overflow
-        let expected = GrayImage::from_fn(300, 300, |x, y| Luma([min(255, max(x, y)) as u8]));
+        let expected = GrayImage::from_fn(300, 3, |x, y| Luma([min(255, max(x, y)) as u8]));
 
         let distances = distance_transform(&image, Norm::LInf);
         assert_pixels_eq!(distances, expected);
diff --git a/src/filter/mod.rs b/src/filter/mod.rs
index e0651053..107ea8ae 100644
--- a/src/filter/mod.rs
+++ b/src/filter/mod.rs
@@ -912,15 +912,15 @@ mod tests {
 
     #[test]
     fn test_gaussian_on_u8_white_idempotent() {
-        let image = ImageBuffer::<Luma<u8>, Vec<u8>>::from_pixel(64, 64, Luma([255]));
-        let image2 = gaussian_blur_f32(&image, 10f32);
+        let image = ImageBuffer::<Luma<u8>, Vec<u8>>::from_pixel(12, 12, Luma([255]));
+        let image2 = gaussian_blur_f32(&image, 6f32);
         assert_pixels_eq_within!(image2, image, 0);
     }
 
     #[test]
     fn test_gaussian_on_f32_white_idempotent() {
-        let image = ImageBuffer::<Luma<f32>, Vec<f32>>::from_pixel(64, 64, Luma([1.0]));
-        let image2 = gaussian_blur_f32(&image, 10f32);
+        let image = ImageBuffer::<Luma<f32>, Vec<f32>>::from_pixel(12, 12, Luma([1.0]));
+        let image2 = gaussian_blur_f32(&image, 6f32);
         assert_pixels_eq_within!(image2, image, 1e-6);
     }
 }