diff --git a/src/tiff.rs b/src/tiff.rs
index efe8ced..f7cd11e 100644
--- a/src/tiff.rs
+++ b/src/tiff.rs
@@ -169,4 +169,13 @@ mod tests {
         assert_err_pat!(parse_exif(data),
                         Error::InvalidFormat("Unexpected next IFD"));
     }
+
+    #[test]
+    fn unknown_field() {
+        let data = b"MM\0\x2a\0\0\0\x08\
+                     \0\x01\x01\0\xff\xff\0\0\0\x01\0\x14\0\0\0\0\0\0";
+        let (v, _) = parse_exif(data).unwrap();
+        assert_eq!(v.len(), 1);
+        assert_pat!(v[0].value, Value::Unknown(0xffff, 1, 0x140000));
+    }
 }
diff --git a/src/tmacro.rs b/src/tmacro.rs
index 6a1b090..c100206 100644
--- a/src/tmacro.rs
+++ b/src/tmacro.rs
@@ -35,6 +35,15 @@ macro_rules! assert_ok {
     )
 }
 
+macro_rules! assert_pat {
+    ($expr:expr, $pat:pat) => (
+        match $expr {
+            $pat => {},
+            ref r => panic!("assertion failed: unexpected {:?}", r),
+        }
+    )
+}
+
 macro_rules! assert_err_pat {
     ($expr:expr, $variant:pat) => (
         match $expr {
diff --git a/src/value.rs b/src/value.rs
index 59f2830..ec85441 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -457,4 +457,10 @@ mod tests {
     fn short_oor() {
         parse_short::<BigEndian>(b"\x01\x02\x03\x04", 1, 2);
     }
+
+    #[test]
+    fn unknown() {
+        let (unitlen, _parser) = get_type_info::<BigEndian>(0xffff);
+        assert_eq!(unitlen, 0);
+    }
 }