diff --git a/Modules/flmodule.c b/Modules/flmodule.c
index 143a1ee..277b1fa 100644
--- a/Modules/flmodule.c
+++ b/Modules/flmodule.c
@@ -281,6 +281,8 @@
 	{NULL}	/* Sentinel */
 };
 
+#undef OFF
+
 static object *
 generic_getattr(g, name)
 	genericobject *g;
@@ -1734,6 +1736,8 @@
 	DEL(f);
 }
 
+#define OFF(x) offsetof(FL_FORM, x)
+
 static struct memberlist form_memberlist[] = {
 	{"window",	T_LONG,		OFF(window),	RO},
 	{"w",		T_FLOAT,	OFF(w)},
@@ -1747,6 +1751,8 @@
 	{NULL}	/* Sentinel */
 };
 
+#undef OFF
+
 static object *
 form_getattr(f, name)
 	formobject *f;