diff --git a/README.md b/README.md
index 34974ade..10c50049 100644
--- a/README.md
+++ b/README.md
@@ -167,7 +167,7 @@ An option name must start with a alphabetic character or underscore. For long op
 
 On a C++14 compiler, you can pass a callback function directly to `.add_flag`, while in C++11 mode you'll need to use `.add_flag_function` if you want a callback function. The function will be given the number of times the flag was passed. You can throw a relevant `CLI::ParseError` to signal a failure.
 
-On a compiler that supports C++17's `__has_include`, you can also use `std::optional`, `std::experimental::optional`, and `boost::optional` directly in an `add_option` call. If you don't have `__has_include`, you can define `CLI11_BOOST_OPTIONAL` before including CLI11 to manually add support for `boost::optional`. See [CLI11 Internals] for information on how this was done and how you can add your own converters.
+On a compiler that supports C++17's `__has_include`, you can also use `std::optional`, `std::experimental::optional`, and `boost::optional` directly in an `add_option` call. If you don't have `__has_include`, you can define `CLI11_BOOST_OPTIONAL 1` before including CLI11 to manually add support (or 0 to remove) for `boost::optional`. See [CLI11 Internals] for information on how this was done and how you can add your own converters.
 
 ### Example
 
diff --git a/include/CLI/Optional.hpp b/include/CLI/Optional.hpp
index 88044e9b..a4a03920 100644
--- a/include/CLI/Optional.hpp
+++ b/include/CLI/Optional.hpp
@@ -12,37 +12,37 @@
 
 #if defined(CLI11_CPP17) && __has_include(<optional>) && \
     defined(__cpp_lib_optional) && !defined(CLI11_STD_OPTIONAL)
-#define CLI11_STD_OPTIONAL
+#define CLI11_STD_OPTIONAL 1
 #endif
 
 #if defined(CLI11_CPP14) && __has_include(<experimental/optional>) && \
     !defined(CLI11_EXPERIMENTAL_OPTIONAL)
-#define CLI11_EXPERIMENTAL_OPTIONAL
+#define CLI11_EXPERIMENTAL_OPTIONAL 1
 #endif
 
 #if __has_include(<boost/optional.hpp>) && !defined(CLI11_BOOST_OPTIONAL)
 #include <boost/version.hpp>
 #if BOOST_VERSION >= 105800
-#define CLI11_BOOST_OPTIONAL
+#define CLI11_BOOST_OPTIONAL 1
 #endif
 #endif
 
 #endif
 
-#ifdef CLI11_STD_OPTIONAL
+#if CLI11_STD_OPTIONAL
 #include <optional>
 #endif
-#ifdef CLI11_EXPERIMENTAL_OPTIONAL
+#if CLI11_EXPERIMENTAL_OPTIONAL
 #include <experimental/optional>
 #endif
-#ifdef CLI11_BOOST_OPTIONAL
+#if CLI11_BOOST_OPTIONAL
 #include <boost/optional.hpp>
 #endif
 // [CLI11:verbatim]
 
 namespace CLI {
 
-#ifdef CLI11_STD_OPTIONAL
+#if CLI11_STD_OPTIONAL
 template <typename T> std::istream &operator>>(std::istream &in, std::optional<T> &val) {
     T v;
     in >> v;
@@ -51,7 +51,7 @@ template <typename T> std::istream &operator>>(std::istream &in, std::optional<T
 }
 #endif
 
-#ifdef CLI11_EXPERIMENTAL_OPTIONAL
+#if CLI11_EXPERIMENTAL_OPTIONAL
 template <typename T> std::istream &operator>>(std::istream &in, std::experimental::optional<T> &val) {
     T v;
     in >> v;
@@ -60,7 +60,7 @@ template <typename T> std::istream &operator>>(std::istream &in, std::experiment
 }
 #endif
 
-#ifdef CLI11_BOOST_OPTIONAL
+#if CLI11_BOOST_OPTIONAL
 template <typename T> std::istream &operator>>(std::istream &in, boost::optional<T> &val) {
     T v;
     in >> v;
@@ -70,17 +70,17 @@ template <typename T> std::istream &operator>>(std::istream &in, boost::optional
 #endif
 
 // Export the best optional to the CLI namespace
-#if defined(CLI11_STD_OPTIONAL)
+#if CLI11_STD_OPTIONAL
 using std::optional;
-#elif defined(CLI11_EXPERIMENTAL_OPTIONAL)
+#elif CLI11_EXPERIMENTAL_OPTIONAL
 using std::experimental::optional;
-#elif defined(CLI11_BOOST_OPTIONAL)
+#elif CLI11_BOOST_OPTIONAL
 using boost::optional;
 #endif
 
 // This is true if any optional is found
-#if defined(CLI11_STD_OPTIONAL) || defined(CLI11_EXPERIMENTAL_OPTIONAL) || defined(CLI11_BOOST_OPTIONAL)
-#define CLI11_OPTIONAL
+#if CLI11_STD_OPTIONAL || CLI11_EXPERIMENTAL_OPTIONAL || CLI11_BOOST_OPTIONAL
+#define CLI11_OPTIONAL 1
 #endif
 
 } // namespace CLI
diff --git a/tests/OptionalTest.cpp b/tests/OptionalTest.cpp
index b67e4ade..6c519e1f 100644
--- a/tests/OptionalTest.cpp
+++ b/tests/OptionalTest.cpp
@@ -3,7 +3,7 @@
 
 #include "app_helper.hpp"
 
-#ifdef CLI11_STD_OPTIONAL
+#if CLI11_STD_OPTIONAL
 
 TEST_F(TApp, StdOptionalTest) {
     std::optional<int> opt;
@@ -25,7 +25,7 @@ TEST_F(TApp, StdOptionalTest) {
 }
 
 #endif
-#ifdef CLI11_EXPERIMENTAL_OPTIONAL
+#if CLI11_EXPERIMENTAL_OPTIONAL
 
 TEST_F(TApp, ExperimentalOptionalTest) {
     std::experimental::optional<int> opt;
@@ -47,7 +47,7 @@ TEST_F(TApp, ExperimentalOptionalTest) {
 }
 
 #endif
-#ifdef CLI11_BOOST_OPTIONAL
+#if CLI11_BOOST_OPTIONAL
 
 TEST_F(TApp, BoostOptionalTest) {
     boost::optional<int> opt;
@@ -70,6 +70,6 @@ TEST_F(TApp, BoostOptionalTest) {
 
 #endif
 
-#ifndef CLI11_OPTIONAL
+#if !CLI11_OPTIONAL
 TEST_F(TApp, DISABLED_OptionalTest) {}
 #endif
diff --git a/tests/informational.cpp b/tests/informational.cpp
index 89c73ff9..b5a0098c 100644
--- a/tests/informational.cpp
+++ b/tests/informational.cpp
@@ -28,21 +28,21 @@ int main() {
     std::cout << "no\n";
 #endif
 
-#ifdef CLI11_OPTIONAL
+#if CLI11_OPTIONAL
     std::cout << "  [Available as CLI::optional]";
 #else
     std::cout << "  No optional library found\n";
 #endif
 
-#ifdef CLI11_STD_OPTIONAL
+#if CLI11_STD_OPTIONAL
     std::cout << "  std::optional support active\n";
 #endif
 
-#ifdef CLI11_EXPERIMENTAL_OPTIONAL
+#if CLI11_EXPERIMENTAL_OPTIONAL
     std::cout << "  std::experimental::optional support active\n";
 #endif
 
-#ifdef CLI11_BOOST_OPTIONAL
+#if CLI11_BOOST_OPTIONAL
     std::cout << "  boost::optional support active\n";
 #endif