diff --git a/perl/xs-src/unpack.c b/perl/xs-src/unpack.c
index 9500212c..dce6782c 100644
--- a/perl/xs-src/unpack.c
+++ b/perl/xs-src/unpack.c
@@ -50,8 +50,7 @@ static int template_execute(msgpack_unpack_t* u PERL_UNUSED_DECL,
 
 STATIC_INLINE SV* template_callback_root(unpack_user* u PERL_UNUSED_DECL)
 {
-    dTHX;
-    return &PL_sv_undef;
+    return NULL;
 }
 
 STATIC_INLINE int template_callback_uint8(unpack_user* u PERL_UNUSED_DECL, uint8_t d, SV** o)
@@ -310,7 +309,7 @@ STATIC_INLINE SV* _execute_impl(SV* self, SV* data, UV off, size_t limit) {
 XS(xs_unpacker_execute) {
     dXSARGS;
     if (items != 3) {
-        Perl_croak(aTHX_ "Usage: $unpacker->execute_limit(data, off)");
+        Perl_croak(aTHX_ "Usage: $unpacker->execute(data, off)");
     }
 
 	UNPACKER(ST(0), mp);
@@ -398,8 +397,8 @@ XS(xs_unpacker_destroy) {
     }
 
 	UNPACKER(ST(0), mp);
-    SV * data = template_data(mp);
-    if (SvOK(data)) {
+    SV* const data = template_data(mp);
+    if (data) {
         SvREFCNT_dec(data);
     }
     Safefree(mp);