-#define av_dup(s,t) (AV*)sv_dup((SV*)s,t)
-#define av_dup_inc(s,t) (AV*)SvREFCNT_inc(sv_dup((SV*)s,t))
-#define hv_dup(s,t) (HV*)sv_dup((SV*)s,t)
-#define hv_dup_inc(s,t) (HV*)SvREFCNT_inc(sv_dup((SV*)s,t))
-#define cv_dup(s,t) (CV*)sv_dup((SV*)s,t)
-#define cv_dup_inc(s,t) (CV*)SvREFCNT_inc(sv_dup((SV*)s,t))
-#define io_dup(s,t) (IO*)sv_dup((SV*)s,t)
-#define io_dup_inc(s,t) (IO*)SvREFCNT_inc(sv_dup((SV*)s,t))
-#define gv_dup(s,t) (GV*)sv_dup((SV*)s,t)
-#define gv_dup_inc(s,t) (GV*)SvREFCNT_inc(sv_dup((SV*)s,t))
+#define av_dup(s,t) MUTABLE_AV(sv_dup((const SV *)s,t))
+#define av_dup_inc(s,t) MUTABLE_AV(SvREFCNT_inc(sv_dup((const SV *)s,t)))
+#define hv_dup(s,t) MUTABLE_HV(sv_dup((const SV *)s,t))
+#define hv_dup_inc(s,t) MUTABLE_HV(SvREFCNT_inc(sv_dup((const SV *)s,t)))
+#define cv_dup(s,t) MUTABLE_CV(sv_dup((const SV *)s,t))
+#define cv_dup_inc(s,t) MUTABLE_CV(SvREFCNT_inc(sv_dup((const SV *)s,t)))
+#define io_dup(s,t) MUTABLE_IO(sv_dup((const SV *)s,t))
+#define io_dup_inc(s,t) MUTABLE_IO(SvREFCNT_inc(sv_dup((const SV *)s,t)))
+#define gv_dup(s,t) MUTABLE_GV(sv_dup((const SV *)s,t))
+#define gv_dup_inc(s,t) MUTABLE_GV(SvREFCNT_inc(sv_dup((const SV *)s,t)))