diff --git a/.travis.yml b/.travis.yml
index 532be9d6..8d9c527f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,7 @@ script:
   - cargo build --verbose
   - cargo test --verbose
   - cargo doc --verbose
+  - ([ $TRAVIS_RUST_VERSION != nightly ] || cargo test --features heap_size)
 
 after_success: |
   [ $TRAVIS_RUST_VERSION = nightly ] &&
diff --git a/Cargo.toml b/Cargo.toml
index d2725565..da6848ab 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,10 +22,18 @@ optional = true
 [dependencies.serde_macros]
 optional = true
 
+[dependencies.heapsize]
+version = "0.1.1"
+optional = true
+
+[dependencies.heapsize_plugin]
+version = "0.0.1"
+optional = true
+
 [dependencies]
 encoding = "0.2"
 matches = "0.1"
 
 [features]
 serde-serialization = [ "serde", "serde_macros" ]
-
+heap_size = [ "heapsize", "heapsize_plugin" ]
diff --git a/src/color.rs b/src/color.rs
index 31debed9..c91b5b7b 100644
--- a/src/color.rs
+++ b/src/color.rs
@@ -11,6 +11,7 @@ use super::{Token, Parser, ToCss};
 /// A color with red, green, blue, and alpha components.
 #[derive(Clone, Copy, PartialEq, Debug)]
 #[cfg_attr(feature = "serde-serialization", derive(Deserialize, Serialize))]
+#[cfg_attr(feature = "heap_size", derive(HeapSizeOf))]
 pub struct RGBA {
     /// The red channel. Nominally in 0.0 ... 1.0.
     pub red: f32,
@@ -41,6 +42,7 @@ impl ToCss for RGBA {
 
 /// A <color> value.
 #[derive(Clone, Copy, PartialEq, Debug)]
+#[cfg_attr(feature = "heap_size", derive(HeapSizeOf))]
 pub enum Color {
     /// The 'currentColor' keyword
     CurrentColor,
diff --git a/src/lib.rs b/src/lib.rs
index e63f38bd..cb0459e4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -9,6 +9,9 @@
 #![cfg_attr(feature = "serde-serialization", feature(custom_derive))]
 #![cfg_attr(feature = "serde-serialization", feature(plugin))]
 #![cfg_attr(feature = "serde-serialization", plugin(serde_macros))]
+#![cfg_attr(feature = "heap_size", feature(custom_derive))]
+#![cfg_attr(feature = "heap_size", feature(plugin))]
+#![cfg_attr(feature = "heap_size", plugin(heapsize_plugin))]
 
 /*!
 
@@ -71,6 +74,7 @@ extern crate encoding;
 #[cfg(test)] extern crate tempdir;
 #[cfg(test)] extern crate rustc_serialize;
 #[cfg(feature = "serde-serialization")] extern crate serde;
+#[cfg(feature = "heap_size")] extern crate heapsize;
 
 pub use tokenizer::{Token, NumericValue, PercentageValue, SourceLocation};
 pub use rules_and_declarations::{parse_important};