diff --git a/example/main/c/main.c b/example/main/c/main.c
index c75d457..5080c30 100644
--- a/example/main/c/main.c
+++ b/example/main/c/main.c
@@ -69,5 +69,17 @@ plugin_main ()
   println ("Rust returned: %s", hi);
   string_free (hi);
 
+  // The API also has full support for custom types (the `Dog` and `TrainedDog`
+  // types are defined in the `api.tri` file)
+  struct Dog dog = { .name = "Bruce" };
+  struct TrainedDog tDog;
+  if (!one.train_dog (&tDog, dog))
+    handle_error ();
+
+  println ("Dog %s is now trained with specialization %i", tDog.name,
+           tDog.training);
+  // Beware that you need to free them with the appropriate free functions
+  string_free (tDog.name);
+
   return 0;
 }
diff --git a/example/main/src/bin/main/api.tri b/example/main/src/bin/main/api.tri
index 981bc02..b2a0eac 100644
--- a/example/main/src/bin/main/api.tri
+++ b/example/main/src/bin/main/api.tri
@@ -22,9 +22,38 @@
 /// Call out an outstanding person
 fn outstanding(name: String);
 
+enum DogTraining {
+    Sheep,
+    Wolf,
+    Blind,
+}
+
+#[error]
+enum TrainingMistake {
+    #[msg("The dog got bitten")]
+    GotBitten,
+    #[msg("The trainer died")]
+    Died,
+}
+
 mod one {
+    /// A Dog after extensive training
+    struct TrainedDog {
+        name: String,
+        training: DogTraining,
+    }
     /// Say hi to a name
     fn hi(name: String) -> String;
+
+    /// Train a dog without using any resources
+    // fn cheaply_train_dog(dog: Dog) -> Result<TrainedDog, TrainingMistake>;
+
+    /// Train a dog
+    fn train_dog(dog: Dog) -> TrainedDog;
+}
+
+struct Dog {
+    name: String,
 }
 
 // Trixy is a subset of Rust