diff -r bb94f6222fef Modules/xxlimited.c
--- a/Modules/xxlimited.c	Wed Dec 19 14:33:35 2012 +0200
+++ b/Modules/xxlimited.c	Wed Dec 19 19:30:32 2012 +0000
@@ -10,7 +10,14 @@
    your own types of attributes instead.  Maybe you want to name your
    local variables other than 'self'.  If your object type is needed in
    other files, you'll have to create a file "foobarobject.h"; see
-   floatobject.h for an example. */
+   floatobject.h for an example.
+
+   This example uses the Py_LIMITED_API API.  See xxlimited.c for a version
+   that doesn't. */
+
+#ifndef Py_LIMITED_API
+# error "This file requires Py_LIMITED_API"
+#endif
 
 /* Xxo objects */
 
diff -r bb94f6222fef Modules/xxmodule.c
--- a/Modules/xxmodule.c	Wed Dec 19 14:33:35 2012 +0200
+++ b/Modules/xxmodule.c	Wed Dec 19 19:30:32 2012 +0000
@@ -10,7 +10,10 @@
    your own types of attributes instead.  Maybe you want to name your
    local variables other than 'self'.  If your object type is needed in
    other files, you'll have to create a file "foobarobject.h"; see
-   floatobject.h for an example. */
+   floatobject.h for an example.
+
+   This example does not use the Py_LIMITED_API API.  See xxlimited.c for
+   a version that does. */
 
 /* Xxo objects */