diff --git a/Cargo.toml b/Cargo.toml
index 23ad063e0..242f05b6c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "serde_json"
-version = "1.0.135"
+version = "1.0.137"
 authors = ["Erick Tryzelaar <erick.tryzelaar@gmail.com>", "David Tolnay <dtolnay@gmail.com>"]
 categories = ["encoding", "parser-implementations", "no-std"]
 description = "A JSON serialization file format"
@@ -38,7 +38,7 @@ targets = ["x86_64-unknown-linux-gnu"]
 rustdoc-args = ["--generate-link-to-definition"]
 
 [package.metadata.playground]
-features = ["raw_value"]
+features = ["float_roundtrip", "raw_value", "unbounded_depth"]
 
 
 ### FEATURES #################################################################
diff --git a/src/lib.rs b/src/lib.rs
index 60a26ca8c..07090dd0c 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -299,7 +299,7 @@
 //! [macro]: crate::json
 //! [`serde-json-core`]: https://github.com/rust-embedded-community/serde-json-core
 
-#![doc(html_root_url = "https://docs.rs/serde_json/1.0.135")]
+#![doc(html_root_url = "https://docs.rs/serde_json/1.0.137")]
 // Ignored clippy lints
 #![allow(
     clippy::collapsible_else_if,
diff --git a/src/value/ser.rs b/src/value/ser.rs
index a68193437..1ffe7b7f1 100644
--- a/src/value/ser.rs
+++ b/src/value/ser.rs
@@ -261,9 +261,9 @@ impl serde::Serializer for Serializer {
         })
     }
 
-    fn serialize_map(self, _len: Option<usize>) -> Result<Self::SerializeMap> {
+    fn serialize_map(self, len: Option<usize>) -> Result<Self::SerializeMap> {
         Ok(SerializeMap::Map {
-            map: Map::new(),
+            map: Map::with_capacity(len.unwrap_or(0)),
             next_key: None,
         })
     }