--- Modules/_ctypes/callproc.c.orig	2008-02-20 02:50:36.000000000 +0100
+++ Modules/_ctypes/callproc.c	2008-02-20 02:52:08.000000000 +0100
@@ -554,6 +554,12 @@
 	}
 #endif
 
+	if (PyFloat_Check(obj)) {
+		pa->ffi_type = &ffi_type_double;
+		pa->value.d = PyFloat_AsDouble(obj);
+		return 0;
+	}
+
 	{
 		PyObject *arg;
 		arg = PyObject_GetAttrString(obj, "_as_parameter_");