diff --git a/README.md b/README.md
index fe5d060a..886ca66f 100644
--- a/README.md
+++ b/README.md
@@ -79,6 +79,8 @@ more information.
 
 ## System requirements
 
+GLFW is written in C99 and does not support Visual Studio 2012 or earlier.
+
 GLFW supports Windows XP and later and macOS 10.8 and later.  Linux and other
 Unix-like systems running the X Window System are supported even without
 a desktop environment or modern extensions, although some features require
diff --git a/docs/compile.dox b/docs/compile.dox
index 4968af40..ecf199a5 100644
--- a/docs/compile.dox
+++ b/docs/compile.dox
@@ -7,6 +7,8 @@
 This is about compiling the GLFW library itself.  For information on how to
 build applications that use GLFW, see @ref build_guide.
 
+GLFW uses some C99 features and does not support Visual Studio 2012 and earlier.
+
 
 @section compile_cmake Using CMake