diff --git a/src/host.rs b/src/host.rs
index 09b6c85..ad5d854 100644
--- a/src/host.rs
+++ b/src/host.rs
@@ -34,7 +34,7 @@ impl<'a> RuntimeArgs<'a> {
 }
 
 /// Custom user error.
-pub trait HostError: 'static + ::std::fmt::Display + ::std::fmt::Debug {
+pub trait HostError: 'static + ::std::fmt::Display + ::std::fmt::Debug + Send + Sync {
 	#[doc(hidden)]
 	fn __private_get_type_id__(&self) -> TypeId {
 		TypeId::of::<Self>()
diff --git a/src/tests/mod.rs b/src/tests/mod.rs
index fb33a01..c202910 100644
--- a/src/tests/mod.rs
+++ b/src/tests/mod.rs
@@ -1,2 +1,15 @@
 mod host;
 mod wasm;
+
+use super::Error;
+
+fn assert_send<T: Send>() {}
+fn assert_sync<T: Sync>() {}
+fn assert_std_err_impl<T: ::std::error::Error>() {}
+
+#[test]
+fn assert_error_properties() {
+	assert_send::<Error>();
+	assert_sync::<Error>();
+	assert_std_err_impl::<Error>();
+}