diff --git a/cranelift/entity/Cargo.toml b/cranelift/entity/Cargo.toml
index 0e390b9b7b..d25353da92 100644
--- a/cranelift/entity/Cargo.toml
+++ b/cranelift/entity/Cargo.toml
@@ -11,10 +11,14 @@ readme = "README.md"
 keywords = ["entity", "set", "map"]
 edition = "2018"
 
+[dependencies]
+serde = { version = "1.0.94", features = ["derive"], optional = true }
+
 [features]
 default = ["std"]
 std = []
 core = []
+enable-serde = ["serde"]
 
 [badges]
 maintenance = { status = "experimental" }
diff --git a/cranelift/entity/src/primary.rs b/cranelift/entity/src/primary.rs
index d3fc7470c0..257cb240f4 100644
--- a/cranelift/entity/src/primary.rs
+++ b/cranelift/entity/src/primary.rs
@@ -7,6 +7,8 @@ use core::iter::FromIterator;
 use core::marker::PhantomData;
 use core::ops::{Index, IndexMut};
 use core::slice;
+#[cfg(feature = "enable-serde")]
+use serde::{Deserialize, Serialize};
 use std::boxed::Box;
 use std::vec::Vec;
 
@@ -26,6 +28,7 @@ use std::vec::Vec;
 /// plain slice would make it easier to use incorrectly. To make a slice of a `PrimaryMap`, use
 /// `into_boxed_slice`.
 #[derive(Debug, Clone)]
+#[cfg_attr(feature = "enable-serde", derive(Serialize, Deserialize))]
 pub struct PrimaryMap<K, V>
 where
     K: EntityRef,