diff --git a/docs/doxygen/mainpages/const_cpp.h b/docs/doxygen/mainpages/const_cpp.h
index f097a08c9e..62408d8461 100644
--- a/docs/doxygen/mainpages/const_cpp.h
+++ b/docs/doxygen/mainpages/const_cpp.h
@@ -199,6 +199,13 @@ Currently the following symbols exist:
 @itemdef{wxHAS_RAW_KEY_CODES, Defined if raw key codes (see wxKeyEvent::GetRawKeyCode are supported.}
 @itemdef{wxHAS_REGEX_ADVANCED, Defined if advanced syntax is available in wxRegEx.}
 @itemdef{wxHAS_TASK_BAR_ICON, Defined if wxTaskBarIcon is available on the current platform.}
+@itemdef{wxHAS_MODE_T, Defined when wxWidgets defines @c mode_t typedef for the
+    compilers not providing it. If another library used in a wxWidgets
+    application, such as ACE (http://www.cs.wustl.edu/~schmidt/ACE.html), also
+    defines @c mode_t, this symbol can be predefined after including the other
+    library header, such as @c "ace/os_include/sys/os_types.h" in ACE case,
+    but before including any wxWidgets headers, to prevent a definition
+    conflict.}
 @endDefList
 
 
diff --git a/include/wx/filefn.h b/include/wx/filefn.h
index 0a7915db07..5a585bd9e5 100644
--- a/include/wx/filefn.h
+++ b/include/wx/filefn.h
@@ -44,7 +44,10 @@
 // constants
 // ----------------------------------------------------------------------------
 
-#if defined(__VISUALC__)
+// MSVC doesn't define mode_t, so do it ourselves unless someone else
+// had already predefined it.
+#if defined(__VISUALC__) && !defined(wxHAS_MODE_T)
+    #define wxHAS_MODE_T
     typedef int mode_t;
 #endif