diff --git a/enumset/src/repr/mod.rs b/enumset/src/repr/mod.rs
index 3f7771c..fc4fc7f 100644
--- a/enumset/src/repr/mod.rs
+++ b/enumset/src/repr/mod.rs
@@ -22,6 +22,8 @@ pub trait EnumSetTypeRepr :
     Eq +
     Debug +
     Hash +
+    Send +
+    Sync +
     // Operations used by enumset
     BitAnd<Output = Self> +
     BitOr<Output = Self> +
diff --git a/enumset/tests/traits.rs b/enumset/tests/traits.rs
new file mode 100644
index 0000000..57be5cf
--- /dev/null
+++ b/enumset/tests/traits.rs
@@ -0,0 +1,15 @@
+#![deny(warnings)]
+
+use enumset::EnumSet;
+use enumset::EnumSetType;
+
+#[test]
+fn send_sync() {
+    #![allow(dead_code)]
+
+    fn drop_thread_safe<T: Send + Sync>(_: T) {}
+
+    fn generic<T: EnumSetType>(set: EnumSet<T>) {
+        drop_thread_safe(set);
+    }
+}