diff --git a/imageio/imageio-jpeg/src/main/java/com/twelvemonkeys/imageio/plugins/jpeg/JPEGImage10Metadata.java b/imageio/imageio-jpeg/src/main/java/com/twelvemonkeys/imageio/plugins/jpeg/JPEGImage10Metadata.java
index 56975a91..f85cb150 100644
--- a/imageio/imageio-jpeg/src/main/java/com/twelvemonkeys/imageio/plugins/jpeg/JPEGImage10Metadata.java
+++ b/imageio/imageio-jpeg/src/main/java/com/twelvemonkeys/imageio/plugins/jpeg/JPEGImage10Metadata.java
@@ -268,7 +268,8 @@ class JPEGImage10Metadata extends AbstractMetadata {
                 default:
                     IIOMetadataNode unknown = new IIOMetadataNode("unknown");
                     unknown.setAttribute("MarkerTag", String.valueOf(segment.marker & 0xFF));
-                    unknown.setUserObject(((Application) segment).data);
+                    byte[] data = segment instanceof Application ? ((Application) segment).data : ((Unknown) segment).data;
+                    unknown.setUserObject(data);
                     markerSequence.appendChild(unknown);
 
                     break;
diff --git a/imageio/imageio-jpeg/src/test/java/com/twelvemonkeys/imageio/plugins/jpeg/JPEGImageReaderTest.java b/imageio/imageio-jpeg/src/test/java/com/twelvemonkeys/imageio/plugins/jpeg/JPEGImageReaderTest.java
index ff8588be..b0dd0994 100644
--- a/imageio/imageio-jpeg/src/test/java/com/twelvemonkeys/imageio/plugins/jpeg/JPEGImageReaderTest.java
+++ b/imageio/imageio-jpeg/src/test/java/com/twelvemonkeys/imageio/plugins/jpeg/JPEGImageReaderTest.java
@@ -114,7 +114,8 @@ public class JPEGImageReaderTest extends ImageReaderAbstractTest<JPEGImageReader
                 new TestData(getClassLoaderResource("/jpeg-lossless/24_ls.jpg"), new Dimension(800, 535)), // Lossless RGB, 8 bit per component (24 bit)
                 new TestData(getClassLoaderResource("/jpeg-lossless/f-18.jpg"), new Dimension(320, 240)), // Lossless RGB, 3 DHTs
                 new TestData(getClassLoaderResource("/jpeg-lossless/testimg_rgb.jpg"), new Dimension(227, 149)), // Lossless RGB, 8 bit per component (24 bit)
-                new TestData(getClassLoaderResource("/jpeg-lossless/testimg_gray.jpg"), new Dimension(512, 512)) // Lossless gray, 16 bit
+                new TestData(getClassLoaderResource("/jpeg-lossless/testimg_gray.jpg"), new Dimension(512, 512)), // Lossless gray, 16 bit
+                new TestData(getClassLoaderResource("/jpeg/dnl-marker.jpg"), new Dimension(194, 132)) // Define Number of Lines marker
         );
 
         // More test data in specific tests below
diff --git a/imageio/imageio-jpeg/src/test/resources/jpeg/dnl-marker.jpg b/imageio/imageio-jpeg/src/test/resources/jpeg/dnl-marker.jpg
new file mode 100644
index 00000000..5050d855
Binary files /dev/null and b/imageio/imageio-jpeg/src/test/resources/jpeg/dnl-marker.jpg differ