diff --git a/Cargo.lock b/Cargo.lock
index 8bedfac..4790d9c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -57,11 +57,17 @@ dependencies = [
  "synstructure 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "fnv"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "hyperjson"
 version = "0.1.0"
 dependencies = [
  "failure 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "fnv 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "pyo3 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -336,6 +342,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "0c4e7bb64a8ebb0d856483e1e682ea3422f883c5f5615a90d51a2c82fe87fdd3"
 "checksum failure 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7efb22686e4a466b1ec1a15c2898f91fa9cb340452496dca654032de20ff95b9"
 "checksum failure_derive 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "946d0e98a50d9831f5d589038d2ca7f8f455b1c21028c0db0e84116a12696426"
+"checksum fnv 1.0.6 (registry+https://github.com/rust-lang/crates.io-index)" = "2fad85553e09a6f881f739c29f0b00b0f01357c743266d478b68951ce23285f3"
 "checksum itoa 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)" = "1306f3464951f30e30d12373d31c79fbd52d236e5e896fd92f96ec7babbbe60b"
 "checksum lazy_static 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ca488b89a5657b0a2ecd45b95609b3e848cf1755da332a0da46e2b2b1cb371a7"
 "checksum libc 0.2.43 (registry+https://github.com/rust-lang/crates.io-index)" = "76e3a3ef172f1a0b9a9ff0dd1491ae5e6c948b94479a3021819ba7d860c8645d"
diff --git a/Cargo.toml b/Cargo.toml
index 97899c2..b03a3f8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,6 +8,7 @@ serde_json = "1.0.13"
 failure = "0.1.1"
 serde = "1.0.53"
 serde_derive = "1.0.53"
+fnv = "1.0.6"
 
 [dependencies.pyo3]
 version = "0.4.0"
diff --git a/src/lib.rs b/src/lib.rs
index 4eba1f3..2597abd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -12,7 +12,9 @@ extern crate serde_derive;
 extern crate pyo3;
 extern crate serde_json;
 
-use std::collections::BTreeMap;
+extern crate fnv;
+
+use fnv::FnvHashMap;
 use std::fmt;
 use std::marker::PhantomData;
 
@@ -20,6 +22,8 @@ use pyo3::prelude::*;
 use serde::de::{self, DeserializeSeed, Deserializer, MapAccess, SeqAccess, Visitor};
 use serde::ser::{self, Serialize, SerializeMap, SerializeSeq, Serializer};
 
+const DEFAULT_HASHMAP_CAPACITY: usize = 10;
+
 #[derive(Debug, Fail)]
 pub enum HyperJsonError {
     #[fail(display = "Conversion error: {}", error)]
@@ -538,7 +542,7 @@ impl<'de, 'a> Visitor<'de> for HyperJsonValue<'a> {
     where
         A: MapAccess<'de>,
     {
-        let mut entries = BTreeMap::new();
+        let mut entries = FnvHashMap::with_capacity_and_hasher(DEFAULT_HASHMAP_CAPACITY, Default::default());
 
         while let Some((key, value)) = map.next_entry_seed(PhantomData::<String>, self)? {
             entries.insert(key, value);