diff --git a/docs/LanguageExtensions.rst b/docs/LanguageExtensions.rst
index 24ef8550c93a88819df17117b852911035071c55..b6933838f07e23dbc50d64916b579242c6b1d452 100644
--- a/docs/LanguageExtensions.rst
+++ b/docs/LanguageExtensions.rst
@@ -1410,9 +1410,11 @@ available in C.
 
 .. code-block:: c++
 
-  int isdigit(int c) __attribute__((enable_if(c >= -1 && c <= 255, "'c' must have the value of an unsigned char or EOF")));
+  int isdigit(int c);
+  int isdigit(int c) __attribute__((enable_if(c <= -1 && c > 255, "chosen when 'c' is out of range"))) __attribute__((unavailable("'c' must have the value of an unsigned char or EOF")));
   
   void foo(char c) {
+    isdigit(c);
     isdigit(10);
     isdigit(-10);  // results in a compile-time error.
   }