diff --git a/src/json/ser.rs b/src/json/ser.rs
index 54c57726..331fbe4a 100644
--- a/src/json/ser.rs
+++ b/src/json/ser.rs
@@ -1,4 +1,3 @@
-use std::{f32, f64};
 use std::io;
 use std::num::{Float, FpCategory};
 use std::string::FromUtf8Error;
@@ -396,7 +395,14 @@ fn fmt_f32_or_null<W>(wr: &mut W, value: f32) -> io::Result<()>
 {
     match value.classify() {
         FpCategory::Nan | FpCategory::Infinite => wr.write_all(b"null"),
-        _ => wr.write_all(f32::to_str_digits(value, 6).as_bytes()),
+        _ => {
+            let s = value.to_string();
+            try!(wr.write_all(s.as_bytes()));
+            if !s.contains('.') {
+                try!(wr.write_all(b".0"))
+            }
+            Ok(())
+        }
     }
 }
 
@@ -405,7 +411,14 @@ fn fmt_f64_or_null<W>(wr: &mut W, value: f64) -> io::Result<()>
 {
     match value.classify() {
         FpCategory::Nan | FpCategory::Infinite => wr.write_all(b"null"),
-        _ => wr.write_all(f64::to_str_digits(value, 6).as_bytes()),
+        _ => {
+            let s = value.to_string();
+            try!(wr.write_all(s.as_bytes()));
+            if !s.contains('.') {
+                try!(wr.write_all(b".0"))
+            }
+            Ok(())
+        }
     }
 }
 
diff --git a/src/lib.rs b/src/lib.rs
index f5de433c..a1d9d717 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,7 +6,7 @@
 //! leaving serde to perform roughly the same speed as a hand written serializer for a specific
 //! type.
 
-#![feature(collections, core, std_misc)]
+#![feature(collections, core)]
 
 
 pub use ser::{Serialize, Serializer};
diff --git a/src/ser/impls.rs b/src/ser/impls.rs
index 75200cf6..c71a1bd7 100644
--- a/src/ser/impls.rs
+++ b/src/ser/impls.rs
@@ -1,4 +1,3 @@
-use std::collections::hash_state::HashState;
 use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet, VecMap};
 use std::hash::Hash;
 use std::path;
@@ -151,9 +150,8 @@ impl<T> Serialize for BTreeSet<T>
     }
 }
 
-impl<T, H> Serialize for HashSet<T, H>
+impl<T> Serialize for HashSet<T>
     where T: Serialize + Eq + Hash,
-          H: HashState,
 {
     #[inline]
     fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
@@ -400,10 +398,9 @@ impl<K, V> Serialize for BTreeMap<K, V>
     }
 }
 
-impl<K, V, H> Serialize for HashMap<K, V, H>
+impl<K, V> Serialize for HashMap<K, V>
     where K: Serialize + Eq + Hash,
           V: Serialize,
-          H: HashState,
 {
     #[inline]
     fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error>
diff --git a/tests/test_json.rs b/tests/test_json.rs
index a87afc76..f7e29791 100644
--- a/tests/test_json.rs
+++ b/tests/test_json.rs
@@ -101,7 +101,7 @@ fn test_write_i64() {
 #[test]
 fn test_write_f64() {
     let tests = &[
-        (3.0, "3"),
+        (3.0, "3.0"),
         (3.1, "3.1"),
         (-1.5, "-1.5"),
         (0.5, "0.5"),