diff --git a/src/librustc/middle/traits/select.rs b/src/librustc/middle/traits/select.rs
index 740bed72d9b..8004cc37ccf 100644
--- a/src/librustc/middle/traits/select.rs
+++ b/src/librustc/middle/traits/select.rs
@@ -39,10 +39,10 @@ use middle::infer;
 use middle::infer::{InferCtxt, TypeFreshener};
 use middle::ty_fold::TypeFoldable;
 use std::cell::RefCell;
-use std::collections::hash_map::HashMap;
 use std::rc::Rc;
 use syntax::{abi, ast};
 use util::common::ErrorReported;
+use util::nodemap::FnvHashMap;
 use util::ppaux::Repr;
 
 pub struct SelectionContext<'cx, 'tcx:'cx> {
@@ -86,8 +86,8 @@ struct TraitObligationStack<'prev, 'tcx: 'prev> {
 
 #[derive(Clone)]
 pub struct SelectionCache<'tcx> {
-    hashmap: RefCell<HashMap<Rc<ty::TraitRef<'tcx>>,
-                             SelectionResult<'tcx, SelectionCandidate<'tcx>>>>,
+    hashmap: RefCell<FnvHashMap<Rc<ty::TraitRef<'tcx>>,
+                                SelectionResult<'tcx, SelectionCandidate<'tcx>>>>,
 }
 
 pub enum MethodMatchResult {
@@ -2634,7 +2634,7 @@ impl<'tcx> Repr<'tcx> for SelectionCandidate<'tcx> {
 impl<'tcx> SelectionCache<'tcx> {
     pub fn new() -> SelectionCache<'tcx> {
         SelectionCache {
-            hashmap: RefCell::new(HashMap::new())
+            hashmap: RefCell::new(FnvHashMap())
         }
     }
 }