--- GType.xs	02 Jun 2008 09:38:05 +1000	1.92
+++ GType.xs	20 Jun 2008 18:10:11 +1000	
@@ -2773,7 +2773,7 @@
         RETVAL
 
 SV *
-union (SV *a, SV *b, int swap)
+union (SV *a, SV *b, SV *swap)
     ALIAS:
         sub = 1
         intersect = 2
@@ -2783,12 +2783,13 @@
 {
 	GType gtype;
 	const char *package;
-        gint a_, b_;
+        gint a_, b_, swap_;
 
 	package = sv_reftype (SvRV (a), TRUE);
 	gtype = gperl_fundamental_type_from_package (package);
-        a_ = gperl_convert_flags (gtype, swap ? b : a);
-        b_ = gperl_convert_flags (gtype, swap ? a : b);
+        swap_ = SvTRUE (swap);
+        a_ = gperl_convert_flags (gtype, swap_ ? b : a);
+        b_ = gperl_convert_flags (gtype, swap_ ? a : b);
 
         switch (ix) {
           case 0: a_ |= b_; break;