diff --git a/bin/pt-archiver b/bin/pt-archiver
index be2a7d4e..01e42a22 100755
--- a/bin/pt-archiver
+++ b/bin/pt-archiver
@@ -1104,14 +1104,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -1285,7 +1286,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/bin/pt-deadlock-logger b/bin/pt-deadlock-logger
index b5a35c53..864eb94a 100755
--- a/bin/pt-deadlock-logger
+++ b/bin/pt-deadlock-logger
@@ -1101,14 +1101,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -1282,7 +1283,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/bin/pt-kill b/bin/pt-kill
index d6cc6ccb..72c9f3f8 100755
--- a/bin/pt-kill
+++ b/bin/pt-kill
@@ -1108,14 +1108,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -1289,7 +1290,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/bin/pt-online-schema-change b/bin/pt-online-schema-change
index de3bd493..a1170a48 100755
--- a/bin/pt-online-schema-change
+++ b/bin/pt-online-schema-change
@@ -1114,14 +1114,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -1295,7 +1296,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/bin/pt-slave-delay b/bin/pt-slave-delay
index 09fe421f..c67d286f 100755
--- a/bin/pt-slave-delay
+++ b/bin/pt-slave-delay
@@ -1101,14 +1101,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -1282,7 +1283,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/bin/pt-slave-find b/bin/pt-slave-find
index 847f87f2..12013bed 100755
--- a/bin/pt-slave-find
+++ b/bin/pt-slave-find
@@ -1080,14 +1080,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -1261,7 +1262,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/bin/pt-slave-restart b/bin/pt-slave-restart
index e8edcc6a..bbfb40f6 100755
--- a/bin/pt-slave-restart
+++ b/bin/pt-slave-restart
@@ -1222,14 +1222,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -1403,7 +1404,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/bin/pt-table-checksum b/bin/pt-table-checksum
index d0159e39..5f92d279 100755
--- a/bin/pt-table-checksum
+++ b/bin/pt-table-checksum
@@ -2774,14 +2774,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -2955,7 +2956,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/bin/pt-variable-advisor b/bin/pt-variable-advisor
index b2e32e02..0d89b67a 100755
--- a/bin/pt-variable-advisor
+++ b/bin/pt-variable-advisor
@@ -1105,14 +1105,15 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
+
 
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
    map {
@@ -1286,7 +1287,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/lib/Mo.pm b/lib/Mo.pm
index cbc5764e..ba96a512 100644
--- a/lib/Mo.pm
+++ b/lib/Mo.pm
@@ -41,19 +41,19 @@ use strict;
 use warnings qw( FATAL all );
 
 use Carp ();
-use Scalar::Util ();
+use Scalar::Util qw(looks_like_number blessed);
 
 # Basic types for isa. If you want a new type, either add it here,
 # or give isa a coderef.
+
 our %TYPES = (
-   Bool   => sub { !$_[0] || (defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == 1) },
-   Num    => sub { defined $_[0] && &Scalar::Util::looks_like_number },
-   Int    => sub { defined $_[0] && &Scalar::Util::looks_like_number && $_[0] == int $_[0] },
+   Bool   => sub { !$_[0] || (defined $_[0] && looks_like_number($_[0]) && $_[0] == 1) },
+   Num    => sub { defined $_[0] && looks_like_number($_[0]) },
+   Int    => sub { defined $_[0] && looks_like_number($_[0]) && $_[0] == int($_[0]) },
    Str    => sub { defined $_[0] },
-   Object => sub { defined $_[0] && &Scalar::Util::blessed },
+   Object => sub { defined $_[0] && blessed($_[0]) },
    FileHandle => sub { local $@; require IO::Handle; fileno($_[0]) && $_[0]->opened },
 
-   # Ref types:
    map {
       my $type = /R/ ? $_ : uc $_;
       $_ . "Ref" => sub { ref $_[0] eq $type }
@@ -245,7 +245,7 @@ sub Mo::import {
                   $method = sub {
                      if ( $#_ ) {
                         Carp::confess(qq<Attribute ($attribute) doesn't consume a '$role' role">)
-                           unless blessed($_[1]) && $_[1]->does($role)
+                           unless Scalar::Util::blessed($_[1]) && eval { $_[1]->does($role) }
                      }
                      goto &$original_method
                   };
diff --git a/t/lib/Mo/isa.t b/t/lib/Mo/isa.t
index 39e4e19c..426c2cb9 100644
--- a/t/lib/Mo/isa.t
+++ b/t/lib/Mo/isa.t
@@ -9,6 +9,7 @@ BEGIN {
 use strict;
 use warnings FATAL => 'all';
 use English qw(-no_match_vars);
+use PerconaTest ();
 use Test::More;
 
 sub dies_ok (&;$) {
@@ -182,4 +183,19 @@ for my $type (@types[1..$#types]) {
     my $method = "my$type";
     dies_ok { $foo->$method(undef) } "$type attr set to undef dies" }
 
+
+use Config;
+use File::Spec;
+use IPC::Cmd ();
+my $thisperl = $^X;
+if ($^O ne 'VMS')
+   {$thisperl .= $Config{_exe} unless $thisperl =~ m/$Config{_exe}$/i;}
+
+my $pm_test = "$PerconaTest::trunk/t/lib/Mo/isa_subtest.pm";
+   
+ok(
+   scalar(IPC::Cmd::run(command => [$thisperl, $pm_test])),
+   "Mo types work with Scalar::Util::PP",
+);
+
 done_testing;
diff --git a/t/lib/Mo/isa_subtest.pm b/t/lib/Mo/isa_subtest.pm
new file mode 100644
index 00000000..1f331b93
--- /dev/null
+++ b/t/lib/Mo/isa_subtest.pm
@@ -0,0 +1,28 @@
+BEGIN {
+   require Scalar::Util::PP;
+   *Scalar::Util:: = \*Scalar::Util::PP::;
+   $INC{"Scalar/Util.pm"} = __FILE__;
+};
+
+BEGIN {
+   die "The PERCONA_TOOLKIT_BRANCH environment variable is not set.\n"
+      unless $ENV{PERCONA_TOOLKIT_BRANCH} && -d $ENV{PERCONA_TOOLKIT_BRANCH};
+   unshift @INC, "$ENV{PERCONA_TOOLKIT_BRANCH}/lib";
+};
+
+use strict;
+use warnings;
+
+{
+   package isa_subtest;
+   use Mo;
+
+   has attr => (
+      is  => 'rw',
+      isa => 'Int',
+   );
+
+   1;
+}
+
+isa_subtest->new(attr => 100);