diff --git a/Rakefile b/Rakefile
index e29ba3e0..de4d4f08 100644
--- a/Rakefile
+++ b/Rakefile
@@ -92,7 +92,7 @@ rust_tests :platformtree_test, {
 
 rust_tests :zinc_test, {
   source:  'main.rs'.in_source,
-  deps:    [:core_crate],
+  deps:    [:core_crate, :macro_ioreg],
   produce: 'zinc_test'.in_build,
   recompile_on: [:platform],
   build_for: :host,
diff --git a/platformtree/builder/os.rs b/platformtree/builder/os.rs
index a073a8d7..a6986a20 100644
--- a/platformtree/builder/os.rs
+++ b/platformtree/builder/os.rs
@@ -148,7 +148,6 @@ fn build_args(builder: &mut Builder, cx: &mut ExtCtxt,
   }
 
   let name_ident = cx.ident_of(format!("{}_args", struct_name).as_slice());
-  let a_lifetime = cx.lifetime(DUMMY_SP, intern("'a"));
   let mut collected_params = vec!();
   let mut ty_params_vec = vec!();
   for ty in ty_params.iter() {
@@ -173,7 +172,7 @@ fn build_args(builder: &mut Builder, cx: &mut ExtCtxt,
       super_struct: None,
       is_virtual: false,
     }, ast::Generics {
-      lifetimes: vec!(a_lifetime),
+      lifetimes: vec!(cx.lifetime_def(DUMMY_SP, intern("'a"), vec!())),
       ty_params: OwnedSlice::from_vec(collected_params),
     }),
     vis: ast::Public,