diff --git a/doc/api.rst b/doc/api.rst
index ba847ae3..5a93b4aa 100644
--- a/doc/api.rst
+++ b/doc/api.rst
@@ -58,6 +58,36 @@ formatting::
 The format string syntax is described in the documentation of
 `strftime <http://en.cppreference.com/w/cpp/chrono/c/strftime>`_.
 
+Formatting user-defined types
+-----------------------------
+
+A custom ``format_arg`` function may be implemented and used to format any
+user-defined type. That is how date and time formatting described in the
+previous section is implemented in :file:`fmt/time.h`. The following example
+shows how to implement custom formatting for a user-defined structure.
+
+::
+
+  struct MyStruct { double a, b; };
+
+  void format_arg(fmt::BasicFormatter<char> &f,
+    const char *&format_str, const MyStruct &s) {
+    f.writer().write("[MyStruct: a={:.1f}, b={:.2f}]", s.a, s.b);
+  }
+
+  MyStruct m = { 1, 2 };
+  std::string s = fmt::format("m={}", n);
+  // s == "m=[MyStruct: a=1.0, b=2.00]"
+
+Note in the example above the ``format_arg`` function ignores the contents of
+``format_str`` so the type will always be formatted as specified. See
+``format_arg`` in :file:`fmt/time.h` for an advanced example of how to use
+the ``format_str`` argument to customize the formatted output.
+
+This section shows how to define a custom format function for a user-defined
+type. The next section describes how to get ``fmt`` to use a conventional stream
+output ``operator<<`` when one is defined for a user-defined type.
+
 ``std::ostream`` support
 ------------------------
 
diff --git a/fmt/format.h b/fmt/format.h
index 4432c770..ae7bd493 100644
--- a/fmt/format.h
+++ b/fmt/format.h
@@ -194,6 +194,17 @@ typedef __int64          intmax_t;
 # endif
 #endif
 
+#ifndef FMT_OVERRIDE
+# if FMT_USE_OVERRIDE || FMT_HAS_FEATURE(cxx_override) || \
+   (FMT_GCC_VERSION >= 408 && FMT_HAS_GXX_CXX11) || \
+   FMT_MSC_VER >= 1900
+#  define FMT_OVERRIDE override
+# else
+#  define FMT_OVERRIDE
+# endif
+#endif
+
+
 // A macro to disallow the copy constructor and operator= functions
 // This should be used in the private: declarations for a class
 #ifndef FMT_USE_DELETED_FUNCTIONS
@@ -678,7 +689,7 @@ class MemoryBuffer : private Allocator, public Buffer<T> {
   }
 
  protected:
-  void grow(std::size_t size);
+  void grow(std::size_t size) FMT_OVERRIDE;
 
  public:
   explicit MemoryBuffer(const Allocator &alloc = Allocator())
diff --git a/fmt/posix.h b/fmt/posix.h
index 7c2b0b5e..d4cd1198 100644
--- a/fmt/posix.h
+++ b/fmt/posix.h
@@ -10,7 +10,7 @@
 #ifndef FMT_POSIX_H_
 #define FMT_POSIX_H_
 
-#ifdef __MINGW32__
+#if defined(__MINGW32__) || defined(__CYGWIN__)
 // Workaround MinGW bug https://sourceforge.net/p/mingw/bugs/2024/.
 # undef __STRICT_ANSI__
 #endif
@@ -302,7 +302,8 @@ class File {
 // Returns the memory page size.
 long getpagesize();
 
-#if (defined(LC_NUMERIC_MASK) || defined(_MSC_VER)) && !defined(__ANDROID__)
+#if (defined(LC_NUMERIC_MASK) || defined(_MSC_VER)) && \
+    !defined(__ANDROID__) && !defined(__CYGWIN__)
 # define FMT_LOCALE
 #endif