diff --git a/CMakeLists.txt b/CMakeLists.txt
index d765423a..3b2abc80 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -122,7 +122,7 @@ endif ()
 check_cxx_source_compiles("
   int main(){int*p=nullptr;}" FMT_NULLPTR)
 if (FMT_NULLPTR)
-  add_definitions(-DFMT_USE_NULLPTR=1)
+# add_definitions(-DFMT_USE_NULLPTR=1)
 endif ()
 
 check_cxx_source_compiles("
@@ -133,14 +133,14 @@ check_cxx_source_compiles("
   };
   int main(){}" FMT_DELETED_FUNCTIONS)
 if (FMT_DELETED_FUNCTIONS)
-  add_definitions(-DFMT_USE_DELETED_FUNCTIONS=1)
+# add_definitions(-DFMT_USE_DELETED_FUNCTIONS=1)
 endif ()
 
 check_cxx_source_compiles("
   void f() noexcept {}
   int main(){ f(); }" FMT_BASIC_NOEXCEPT_SUPPORT)
 if (FMT_BASIC_NOEXCEPT_SUPPORT)
-  add_definitions(-DFMT_USE_NOEXCEPT=1)
+# add_definitions(-DFMT_USE_NOEXCEPT=1)
 endif ()
 
 check_cxx_source_compiles("
@@ -157,7 +157,7 @@ check_cxx_source_compiles("
     MoveOnly c(MoveOnly());
   }" FMT_RVALUE_REFERENCES)
 if (FMT_RVALUE_REFERENCES)
-  add_definitions(-DFMT_USE_RVALUE_REFERENCES=1)
+# add_definitions(-DFMT_USE_RVALUE_REFERENCES=1)
 endif ()
 
 # GTest doesn't detect <tuple> with clang.
diff --git a/format.h b/format.h
index a837f6a1..1a6ff0e6 100644
--- a/format.h
+++ b/format.h
@@ -137,25 +137,9 @@
     || (FMT_GCC_VERSION >= 406 && __cplusplus >= 201103L)\
     || (_MSC_VER >= 1600)
 // Use nullptr
-#else
-// Simulate it
-namespace std {
-class nullptr_t {
-public:
-  template<typename T>
-  operator T*() const {
-    return 0;
-  }
-  template<typename C, typename T>
-  operator T C::*() const {
-    return 0;
-  }
-private:
-  void operator&() const;
-};
-}
-
-std::nullptr_t const nullptr = {};
+#elif !defined(nullptr)
+// Some standard library implementations define nullptr themselves such as libc++
+# define nullptr 0
 #endif
 
 namespace fmt {