diff --git a/include/CLI/Optional.hpp b/include/CLI/Optional.hpp
index 6370c45..1597da3 100644
--- a/include/CLI/Optional.hpp
+++ b/include/CLI/Optional.hpp
@@ -35,7 +35,7 @@
 namespace CLI {
 
 #ifdef CLI11_STD_OPTIONAL
-template <typename T> std::istringstream &operator>>(std::istringstream &in, std::optional<T> &val) {
+template <typename T> std::istream &operator>>(std::istream &in, std::optional<T> &val) {
     T v;
     in >> v;
     val = v;
@@ -44,7 +44,7 @@ template <typename T> std::istringstream &operator>>(std::istringstream &in, std
 #endif
 
 #ifdef CLI11_EXPERIMENTAL_OPTIONAL
-template <typename T> std::istringstream &operator>>(std::istringstream &in, std::experimental::optional<T> &val) {
+template <typename T> std::istream &operator>>(std::istream &in, std::experimental::optional<T> &val) {
     T v;
     in >> v;
     val = v;
@@ -53,7 +53,7 @@ template <typename T> std::istringstream &operator>>(std::istringstream &in, std
 #endif
 
 #ifdef CLI11_BOOST_OPTIONAL
-template <typename T> std::istringstream &operator>>(std::istringstream &in, boost::optional<T> &val) {
+template <typename T> std::istream &operator>>(std::istream &in, boost::optional<T> &val) {
     T v;
     in >> v;
     val = v;