diff --git a/tests/files/issue-426-01.png b/tests/files/issue-426-01.png
new file mode 100644
index 00000000..7349d388
Binary files /dev/null and b/tests/files/issue-426-01.png differ
diff --git a/tests/files/issue-426-02.png b/tests/files/issue-426-02.png
new file mode 100644
index 00000000..e3031723
Binary files /dev/null and b/tests/files/issue-426-02.png differ
diff --git a/tests/regression.rs b/tests/regression.rs
index 6fb119ca..30797d3d 100644
--- a/tests/regression.rs
+++ b/tests/regression.rs
@@ -642,3 +642,27 @@ fn issue_195() {
         BitDepth::Eight,
     );
 }
+
+#[test]
+fn issue_426_01() {
+    test_it_converts(
+        "tests/files/issue-426-01.png",
+        None,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+        ColorType::Grayscale,
+        BitDepth::One,
+    );
+}
+
+#[test]
+fn issue_426_02() {
+    test_it_converts(
+        "tests/files/issue-426-02.png",
+        None,
+        ColorType::Grayscale,
+        BitDepth::Eight,
+        ColorType::Grayscale,
+        BitDepth::One,
+    );
+}