diff --git a/src/lnf.rs b/src/lnf.rs
index f8b3ad9..9e38aea 100644
--- a/src/lnf.rs
+++ b/src/lnf.rs
@@ -31,7 +31,16 @@ impl TypeTerm {
         match self {
             TypeTerm::Ladder(args) => {
                 for x in args.into_iter() {
-                    new_ladder.push(x.normalize());
+                    match x.normalize() {
+                        TypeTerm::Ladder(gs) => {
+                            for g in gs {
+                                new_ladder.push(g);
+                            }
+                        }
+                        g => {
+                            new_ladder.push(g);
+                        }
+                    }
                 }
             }
 
@@ -102,9 +111,7 @@ impl TypeTerm {
             TypeTerm::Ladder( v ) => {
                 v
             },
-            _ => {
-                unreachable!();
-            }
+            flat => vec![ flat ]
         }
     }
 }
diff --git a/src/test/subtype.rs b/src/test/subtype.rs
index 836b492..54ad397 100644
--- a/src/test/subtype.rs
+++ b/src/test/subtype.rs
@@ -72,5 +72,26 @@ fn test_syntactic_subtype() {
             ),
         Err(None)
     );
+
+    assert_eq!(
+        dict.parse("<Duration Seconds>~ℕ").expect("parse error")
+            .is_syntactic_subtype_of(
+                &dict.parse("ℕ").expect("parse errror")
+            ),
+        Ok(1)
+    );
+
+    assert_eq!(
+        dict.parse("
+<Duration Seconds>
+~ℕ
+~<PosInt 10 BigEndian>
+~< Seq   <Digit 10> ~ Char >"
+        ).expect("parse error")
+            .is_syntactic_subtype_of(
+                &dict.parse("<Seq Char>").expect("parse errror")
+            ),
+        Ok(4)
+    );
 }