diff --git a/include/CLI/Optional.hpp b/include/CLI/Optional.hpp
index 9e1315e6..5b7d3e0b 100644
--- a/include/CLI/Optional.hpp
+++ b/include/CLI/Optional.hpp
@@ -3,7 +3,7 @@
 // Distributed under the 3-Clause BSD License.  See accompanying
 // file LICENSE or https://github.com/CLIUtils/CLI11 for details.
 
-#include <sstream>
+#include <istream>
 
 #include "CLI/Macros.hpp"
 
@@ -15,11 +15,11 @@
 #define CLI11_STD_OPTIONAL
 #endif
 #endif
-#if defined(CPP11_CPP14) && __has_include(<experimental/optional>)
+#if defined(CLI11_CPP14) && __has_include(<experimental/optional>)
 #include <experimental/optional>
 #define CLI11_EXPERIMENTAL_OPTIONAL
 #endif
-#if __has_include(<boost/optional>)
+#if __has_include(<boost/optional.hpp>)
 #include <boost/optional.hpp>
 #define CLI11_BOOST_OPTIONAL
 #endif
@@ -44,16 +44,16 @@ template <typename T> std::istream &operator>>(std::istream &in, std::experiment
     val = v;
     return in;
 }
+#endif
 
 #ifdef CLI11_BOOST_OPTIONAL
-template <typename T> std::istream &operator>>(std::istream &in, boost::optional<T> &val) {
+template <typename T> std::istringstream &operator>>(std::istringstream &in, boost::optional<T> &val) {
     T v;
     in >> v;
     val = v;
     return in;
 }
 #endif
-#endif
 
 // Export the best optional to the CLI namespace
 #if defined(CLI11_STD_OPTIONAL)
diff --git a/tests/OptionalTest.cpp b/tests/OptionalTest.cpp
index d6767a46..305f4274 100644
--- a/tests/OptionalTest.cpp
+++ b/tests/OptionalTest.cpp
@@ -6,7 +6,7 @@
 #ifdef CLI11_OPTIONAL
 
 TEST_F(TApp, OptionalTest) {
-    optional<int> opt;
+    CLI::optional<int> opt;
     app.add_option("-c,--count", opt);
     run();
     EXPECT_FALSE(opt);
diff --git a/tests/informational.cpp b/tests/informational.cpp
index 5c219baf..89c73ff9 100644
--- a/tests/informational.cpp
+++ b/tests/informational.cpp
@@ -31,8 +31,7 @@ int main() {
 #ifdef CLI11_OPTIONAL
     std::cout << "  [Available as CLI::optional]";
 #else
-        std::cout
-              << "  No optional library found\n";
+    std::cout << "  No optional library found\n";
 #endif
 
 #ifdef CLI11_STD_OPTIONAL