diff --git a/src/identifier.rs b/src/identifier.rs
index 820f5d47..170a4e05 100644
--- a/src/identifier.rs
+++ b/src/identifier.rs
@@ -249,6 +249,9 @@ impl PartialEq for Identifier {
     }
 }
 
+unsafe impl Send for Identifier {}
+unsafe impl Sync for Identifier {}
+
 // We use heap pointers that are 2-byte aligned, meaning they have an
 // insignificant 0 in the least significant bit. We take advantage of that
 // unneeded bit to rotate a 1 into the most significant bit to make the repr
diff --git a/tests/test_autotrait.rs b/tests/test_autotrait.rs
new file mode 100644
index 00000000..af8534bd
--- /dev/null
+++ b/tests/test_autotrait.rs
@@ -0,0 +1,12 @@
+fn assert_send_sync<T: Send + Sync>() {}
+
+#[test]
+fn test() {
+    assert_send_sync::<semver::BuildMetadata>();
+    assert_send_sync::<semver::Comparator>();
+    assert_send_sync::<semver::Error>();
+    assert_send_sync::<semver::Prerelease>();
+    assert_send_sync::<semver::Version>();
+    assert_send_sync::<semver::VersionReq>();
+    assert_send_sync::<semver::Op>();
+}