diff --git a/src/sled/futures/future.h b/src/sled/futures/future.h
index d16181e..701dbc1 100644
--- a/src/sled/futures/future.h
+++ b/src/sled/futures/future.h
@@ -1,6 +1,7 @@
 #ifndef SLED_FUTURES_FUTURE_H
 #define SLED_FUTURES_FUTURE_H
 
+#include <exception>
 #pragma once
 #include "sled/exec/detail/invoke_result.h"
 #include "sled/futures/internal/failure_handling.h"
@@ -59,7 +60,7 @@ struct FutureData {
 
 //
 
-template<typename T, typename FailureT>
+template<typename T, typename FailureT = std::exception>
 class Future {
     static_assert(!std::is_same<T, void>::value, "Future<void, _> is not allowed. Use Future<bool, _> instead");
     static_assert(!std::is_same<FailureT, void>::value, "Future<_, void> is not allowed. Use Future<_, bool> instead");
diff --git a/src/sled/futures/internal/promise.h b/src/sled/futures/internal/promise.h
index b586569..2265a56 100644
--- a/src/sled/futures/internal/promise.h
+++ b/src/sled/futures/internal/promise.h
@@ -10,8 +10,8 @@ namespace sled {
 template<typename T, typename FailureT>
 class Future;
 
-template<typename T, typename FailureT>
-class Promise {
+template<typename T, typename FailureT = std::exception>
+class Promise final {
     static_assert(!std::is_same<T, void>::value, "Promise<void, _> is not allowed. Use Promise<bool, _> instead");
     static_assert(!std::is_same<FailureT, void>::value,
                   "Promise<_, void> is not allowed. Use Promise<_, bool> instead");