diff --git a/src/borrowed.rs b/src/borrowed.rs
index 7e41e06e..5c7443b2 100644
--- a/src/borrowed.rs
+++ b/src/borrowed.rs
@@ -123,7 +123,7 @@ pub trait RedisClientBorrowed {
 
   fn hmget<F: Into<MultipleKeys>, K: Into<RedisKey>>(&self, key: K, fields: F) -> Box<Future<Item=Vec<RedisValue>, Error=RedisError>>;
 
-  fn hmset<V: Into<RedisValue>, F: Into<RedisKey> + Hash + Eq, K: Into<RedisKey>>(&self, key: K, mut values: HashMap<F, V>) -> Box<Future<Item=String, Error=RedisError>>;
+  fn hmset<V: Into<RedisValue>, F: Into<RedisKey> + Hash + Eq, K: Into<RedisKey>>(&self, key: K, values: HashMap<F, V>) -> Box<Future<Item=String, Error=RedisError>>;
 
   fn hset<K: Into<RedisKey>, F: Into<RedisKey>, V: Into<RedisValue>>(&self, key: K, field: F, value: V) -> Box<Future<Item=usize, Error=RedisError>>;
 
diff --git a/src/owned.rs b/src/owned.rs
index e72c1101..1482a71b 100644
--- a/src/owned.rs
+++ b/src/owned.rs
@@ -120,7 +120,7 @@ pub trait RedisClientOwned: Sized {
 
   fn hmget<F: Into<MultipleKeys>, K: Into<RedisKey>>(self, key: K, fields: F) -> Box<Future<Item=(Self, Vec<RedisValue>), Error=RedisError>>;
 
-  fn hmset<V: Into<RedisValue>, F: Into<RedisKey> + Hash + Eq, K: Into<RedisKey>>(self, key: K, mut values: HashMap<F, V>) -> Box<Future<Item=(Self, String), Error=RedisError>>;
+  fn hmset<V: Into<RedisValue>, F: Into<RedisKey> + Hash + Eq, K: Into<RedisKey>>(self, key: K, values: HashMap<F, V>) -> Box<Future<Item=(Self, String), Error=RedisError>>;
 
   fn hset<K: Into<RedisKey>, F: Into<RedisKey>, V: Into<RedisValue>>(self, key: K, field: F, value: V) -> Box<Future<Item=(Self, usize), Error=RedisError>>;