diff --git a/perl/lib/Data/MessagePack.pm b/perl/lib/Data/MessagePack.pm
index ece00505..b1e0174d 100644
--- a/perl/lib/Data/MessagePack.pm
+++ b/perl/lib/Data/MessagePack.pm
@@ -6,22 +6,21 @@ use 5.008001;
 our $VERSION = '0.23';
 our $PreferInteger = 0;
 
-{
-    package
-        Data::MessagePack::Boolean;
-    use overload
-        'bool' => sub { ${ $_[0] } },
-        '0+'   => sub { ${ $_[0] } },
-        '""'   => sub { ${ $_[0] } ? 'true' : 'false' },
-
-        fallback => 1,
-    ;
+sub true () {
+    require Data::MessagePack::Boolean;
+    no warnings 'once', 'redefine';
+    my $t = $Data::MessagePack::Boolean::true;
+    *true = sub (){ $t };
+    return $t;
 }
 
-our $true  = do { bless \(my $dummy = 1), "Data::MessagePack::Boolean" };
-our $false = do { bless \(my $dummy = 0), "Data::MessagePack::Boolean" };
-sub true  () { $true  }
-sub false () { $false }
+sub false () {
+    require Data::MessagePack::Boolean;
+    no warnings 'once', 'redefine';
+    my $f = $Data::MessagePack::Boolean::false;
+    *false = sub (){ $f };
+    return $f;
+}
 
 if ( !__PACKAGE__->can('pack') ) { # this idea comes from Text::Xslate
     my $backend = $ENV{ PERL_DATA_MESSAGEPACK } || '';
diff --git a/perl/lib/Data/MessagePack/Boolean.pm b/perl/lib/Data/MessagePack/Boolean.pm
new file mode 100755
index 00000000..2bb3ecad
--- /dev/null
+++ b/perl/lib/Data/MessagePack/Boolean.pm
@@ -0,0 +1,14 @@
+package Data::MessagePack::Boolean;
+use strict;
+use overload
+    'bool' => sub { ${ $_[0] } },
+    '0+'   => sub { ${ $_[0] } },
+    '""'   => sub { ${ $_[0] } ? 'true' : 'false' },
+
+    fallback => 1,
+;
+
+our $true  = do { bless \(my $dummy = 1) };
+our $false = do { bless \(my $dummy = 0) };
+
+1;
diff --git a/perl/xs-src/MessagePack.c b/perl/xs-src/MessagePack.c
index aba8ef91..69337f41 100644
--- a/perl/xs-src/MessagePack.c
+++ b/perl/xs-src/MessagePack.c
@@ -1,5 +1,9 @@
 #include "xshelper.h"
 
+#ifndef __cplusplus
+#include <stdbool.h>
+#endif
+
 XS(xs_pack);
 XS(xs_unpack);
 XS(xs_unpacker_new);
@@ -10,13 +14,15 @@ XS(xs_unpacker_data);
 XS(xs_unpacker_reset);
 XS(xs_unpacker_destroy);
 
-void boot_Data__MessagePack_pack(void);
+void init_Data__MessagePack_pack(pTHX_ bool const cloning);
+void init_Data__MessagePack_unpack(pTHX_ bool const cloning);
 
 XS(boot_Data__MessagePack) {
     dXSARGS;
     PERL_UNUSED_VAR(items);
 
-    boot_Data__MessagePack_pack();
+    init_Data__MessagePack_pack(aTHX_   false);
+    init_Data__MessagePack_unpack(aTHX_ false);
 
     newXS("Data::MessagePack::pack", xs_pack, __FILE__);
     newXS("Data::MessagePack::unpack", xs_unpack, __FILE__);
diff --git a/perl/xs-src/pack.c b/perl/xs-src/pack.c
index 9a58ed05..862808eb 100644
--- a/perl/xs-src/pack.c
+++ b/perl/xs-src/pack.c
@@ -83,8 +83,7 @@ MGVTBL pref_int_vtbl = {
 #endif
 };
 
-void boot_Data__MessagePack_pack(void) {
-    dTHX;
+void init_Data__MessagePack_pack(pTHX_ bool const cloning) {
     SV* var = get_sv("Data::MessagePack::PreferInteger", 0);
     sv_magicext(var, NULL, PERL_MAGIC_ext, &pref_int_vtbl, NULL, 0);
     SvSETMAGIC(var);
diff --git a/perl/xs-src/unpack.c b/perl/xs-src/unpack.c
index da985e32..6ebb48c2 100644
--- a/perl/xs-src/unpack.c
+++ b/perl/xs-src/unpack.c
@@ -2,6 +2,13 @@
 #define NEED_sv_2pv_flags
 #include "xshelper.h"
 
+#define MY_CXT_KEY "Data::MessagePack::_unpack_guts" XS_VERSION
+typedef struct {
+    SV* msgpack_true;
+    SV* msgpack_false;
+} my_cxt_t;
+START_MY_CXT
+
 typedef struct {
     bool finished;
     bool incremented;
@@ -22,13 +29,52 @@ typedef struct {
 
 #define msgpack_unpack_user unpack_user
 
+void init_Data__MessagePack_unpack(pTHX_ bool const cloning) {
+    if(!cloning) {
+        MY_CXT_INIT;
+        MY_CXT.msgpack_true  = NULL;
+        MY_CXT.msgpack_false = NULL;
+    }
+    else {
+        MY_CXT_CLONE;
+        MY_CXT.msgpack_true  = NULL;
+        MY_CXT.msgpack_false = NULL;
+    }
+}
+
+
+
 /* ---------------------------------------------------------------------- */
 /* utility functions                                                      */
 
-STATIC_INLINE SV *
-get_bool (const char* const name) {
+static SV*
+load_bool(pTHX_ const char* const name) {
+    CV* const cv = get_cv(name, GV_ADD);
+    dSP;
+    PUSHMARK(SP);
+    call_sv((SV*)cv, G_SCALAR);
+    SPAGAIN;
+    SV* const sv = newSVsv(POPs);
+    PUTBACK;
+    return sv;
+}
+
+static SV*
+get_bool(bool const value) {
     dTHX;
-    return newSVsv(get_sv( name, GV_ADD ));
+    dMY_CXT;
+    if(value) {
+        if(!MY_CXT.msgpack_true) {
+            MY_CXT.msgpack_true = load_bool(aTHX_ "Data::MessagePack::true");
+        }
+        return newSVsv(MY_CXT.msgpack_true);
+    }
+    else {
+        if(!MY_CXT.msgpack_false) {
+            MY_CXT.msgpack_false = load_bool(aTHX_ "Data::MessagePack::false");
+        }
+        return newSVsv(MY_CXT.msgpack_false);
+    }
 }
 
 /* ---------------------------------------------------------------------- */
@@ -127,15 +173,13 @@ STATIC_INLINE int template_callback_nil(unpack_user* u PERL_UNUSED_DECL, SV** o)
 
 STATIC_INLINE int template_callback_true(unpack_user* u PERL_UNUSED_DECL, SV** o)
 {
-    dTHX;
-    *o = get_bool("Data::MessagePack::true");
+    *o = get_bool(true);
     return 0;
 }
 
 STATIC_INLINE int template_callback_false(unpack_user* u PERL_UNUSED_DECL, SV** o)
 {
-    dTHX;
-    *o = get_bool("Data::MessagePack::false");
+    *o = get_bool(false);
     return 0;
 }