diff --git a/src/librustc/middle/trans/common.rs b/src/librustc/middle/trans/common.rs
index 78fe4135259..d1be86dfdbe 100644
--- a/src/librustc/middle/trans/common.rs
+++ b/src/librustc/middle/trans/common.rs
@@ -686,22 +686,6 @@ pub fn is_null(val: ValueRef) -> bool {
     }
 }
 
-// Used to identify cached monomorphized functions and vtables
-#[deriving(Eq, TotalEq, Hash)]
-pub struct MonoParamId {
-    pub subst: ty::t,
-    // Do we really need the vtables to be hashed? Isn't the type enough?
-    pub vtables: Vec<mono_id>
-}
-
-#[deriving(Eq, TotalEq, Hash)]
-pub struct mono_id_ {
-    pub def: ast::DefId,
-    pub params: Vec<MonoParamId>
-}
-
-pub type mono_id = @mono_id_;
-
 pub fn monomorphize_type(bcx: &Block, t: ty::t) -> ty::t {
     match bcx.fcx.param_substs {
         Some(substs) => {
diff --git a/src/librustc/middle/trans/context.rs b/src/librustc/middle/trans/context.rs
index 4aad1cded1e..edd801d1347 100644
--- a/src/librustc/middle/trans/context.rs
+++ b/src/librustc/middle/trans/context.rs
@@ -20,8 +20,9 @@ use middle::resolve;
 use middle::trans::adt;
 use middle::trans::base;
 use middle::trans::builder::Builder;
-use middle::trans::common::{mono_id,ExternMap,tydesc_info,BuilderRef_res,Stats};
+use middle::trans::common::{ExternMap,tydesc_info,BuilderRef_res,Stats};
 use middle::trans::debuginfo;
+use middle::trans::monomorphize::MonoId;
 use middle::trans::type_::Type;
 use middle::ty;
 use util::sha2::Sha256;
@@ -61,10 +62,10 @@ pub struct CrateContext {
     /// that is generated
     pub non_inlineable_statics: RefCell<NodeSet>,
     /// Cache instances of monomorphized functions
-    pub monomorphized: RefCell<HashMap<mono_id, ValueRef>>,
+    pub monomorphized: RefCell<HashMap<MonoId, ValueRef>>,
     pub monomorphizing: RefCell<DefIdMap<uint>>,
     /// Cache generated vtables
-    pub vtables: RefCell<HashMap<(ty::t, mono_id), ValueRef>>,
+    pub vtables: RefCell<HashMap<(ty::t, MonoId), ValueRef>>,
     /// Cache of constant strings,
     pub const_cstr_cache: RefCell<HashMap<InternedString, ValueRef>>,
 
diff --git a/src/librustc/middle/trans/monomorphize.rs b/src/librustc/middle/trans/monomorphize.rs
index 16fef63482f..81152523cdd 100644
--- a/src/librustc/middle/trans/monomorphize.rs
+++ b/src/librustc/middle/trans/monomorphize.rs
@@ -16,7 +16,6 @@ use middle::trans::base::{trans_enum_variant, push_ctxt, get_item_val};
 use middle::trans::base::{trans_fn, decl_internal_rust_fn};
 use middle::trans::base;
 use middle::trans::common::*;
-use middle::trans::meth;
 use middle::trans::intrinsic;
 use middle::ty;
 use middle::typeck;
@@ -26,7 +25,7 @@ use syntax::abi;
 use syntax::ast;
 use syntax::ast_map;
 use syntax::ast_util::local_def;
-use std::hash::sip;
+use std::hash::{sip, Hash};
 
 pub fn monomorphic_fn(ccx: &CrateContext,
                       fn_id: ast::DefId,
@@ -71,7 +70,7 @@ pub fn monomorphic_fn(ccx: &CrateContext,
         }).collect()
     };
 
-    let hash_id = @mono_id_ {
+    let hash_id = MonoId {
         def: fn_id,
         params: param_ids
     };
@@ -194,16 +193,22 @@ pub fn monomorphic_fn(ccx: &CrateContext,
     }
 
     let s = ccx.tcx.map.with_path(fn_id.node, |path| {
-        exported_name(path, format!("h{}", sip::hash(&(hash_id, mono_ty))),
+        let mut state = sip::SipState::new();
+        hash_id.hash(&mut state);
+        mono_ty.hash(&mut state);
+
+        exported_name(path, format!("h{}", state.result()),
                       ccx.link_meta.crateid.version_or_default())
     });
     debug!("monomorphize_fn mangled to {}", s);
 
+    // This shouldn't need to option dance.
+    let mut hash_id = Some(hash_id);
     let mk_lldecl = || {
         let lldecl = decl_internal_rust_fn(ccx, false,
                                            f.sig.inputs.as_slice(),
                                            f.sig.output, s);
-        ccx.monomorphized.borrow_mut().insert(hash_id, lldecl);
+        ccx.monomorphized.borrow_mut().insert(hash_id.take_unwrap(), lldecl);
         lldecl
     };
 
@@ -305,21 +310,34 @@ pub fn monomorphic_fn(ccx: &CrateContext,
     (lldecl, false)
 }
 
+// Used to identify cached monomorphized functions and vtables
+#[deriving(Eq, TotalEq, Hash)]
+pub struct MonoParamId {
+    pub subst: ty::t,
+    // Do we really need the vtables to be hashed? Isn't the type enough?
+    pub vtables: Vec<MonoId>
+}
+
+#[deriving(Eq, TotalEq, Hash)]
+pub struct MonoId {
+    pub def: ast::DefId,
+    pub params: Vec<MonoParamId>
+}
+
 pub fn make_vtable_id(ccx: &CrateContext,
                       origin: &typeck::vtable_origin)
-                      -> mono_id {
+                      -> MonoId {
     match origin {
         &typeck::vtable_static(impl_id, ref substs, ref sub_vtables) => {
-            let param_ids = sub_vtables.iter().zip(substs.iter()).map(|(vtable, subst)| {
-                MonoParamId {
-                    subst: *subst,
-                    vtables: vtable.iter().map(|vt| make_vtable_id(ccx, vt)).collect()
-                }
-            }).collect();
-
-            @mono_id_ {
+            MonoId {
                 def: impl_id,
-                params: param_ids
+                params: sub_vtables.iter().zip(substs.iter()).map(|(vtable, subst)| {
+                    MonoParamId {
+                        subst: *subst,
+                        // Do we really need the vtables to be hashed? Isn't the type enough?
+                        vtables: vtable.iter().map(|vt| make_vtable_id(ccx, vt)).collect()
+                    }
+                }).collect()
             }
         }