diff --git a/src/librustc_query_system/query/caches.rs b/src/librustc_query_system/query/caches.rs
index efde51c4db6..400e6fe84a8 100644
--- a/src/librustc_query_system/query/caches.rs
+++ b/src/librustc_query_system/query/caches.rs
@@ -8,12 +8,12 @@ use std::default::Default;
 use std::hash::Hash;
 use std::marker::PhantomData;
 
-pub trait CacheSelector<CTX: QueryContext, K, V> {
+pub trait CacheSelector<CTX: QueryContext, K: Hash, V> {
     type Cache: QueryCache<CTX, Key = K, Value = V>;
 }
 
 pub trait QueryCache<CTX: QueryContext>: Default {
-    type Key;
+    type Key: Hash;
     type Value;
     type Sharded: Default;
 
diff --git a/src/librustc_query_system/query/plumbing.rs b/src/librustc_query_system/query/plumbing.rs
index 6fd86d65c1d..dbe7b9c385d 100644
--- a/src/librustc_query_system/query/plumbing.rs
+++ b/src/librustc_query_system/query/plumbing.rs
@@ -57,9 +57,9 @@ pub struct QueryState<CTX: QueryContext, C: QueryCache<CTX>> {
 }
 
 impl<CTX: QueryContext, C: QueryCache<CTX>> QueryState<CTX, C> {
-    pub(super) fn get_lookup<'tcx, K2: Hash>(
+    pub(super) fn get_lookup<'tcx>(
         &'tcx self,
-        key: &K2,
+        key: &C::Key,
     ) -> QueryLookup<'tcx, CTX, C::Key, C::Sharded> {
         // We compute the key's hash once and then use it for both the
         // shard lookup and the hashmap lookup. This relies on the fact