Update namespaces.md

RexJaeschke · jskeet · commit b1971b23d666 · 2022-06-08T21:58:36.000+01:00
diff --git a/standard/namespaces.md b/standard/namespaces.md
@@ -8,7 +8,7 @@ Using directives ([§13.5](namespaces.md#135-using-directives)) are provided to
 
 ## 13.2 Compilation units
 
-A *compilation_unit* consists of zero or more *extern_alias_directive*s followed by zero or more *using_directive*s followed by zero or more *global_attributes* followed by zero or more *namespace_member_declaration*s. The *compilation_unit* defines the overall structure of the input.
+A *compilation_unit* consists of zero or more *extern_alias_directive*s followed by zero or more *using_directive*s followed by zero or one *global_attributes* followed by zero or more *namespace_member_declaration*s. The *compilation_unit* defines the overall structure of the input.
 
 ```ANTLR
 compilation_unit
