diff --git a/src/core/Cool.pm b/src/core/Cool.pm
index ef35735259f..20a33380942 100644
--- a/src/core/Cool.pm
+++ b/src/core/Cool.pm
@@ -68,11 +68,11 @@ my class Cool { # declared in BOOTSTRAP
 
     ## string methods
 
-    method chars() {
-        nqp::p6box_i(nqp::chars(nqp::unbox_s(self.Str)));
+    method chars() returns Int:D {
+        self.Str.chars
     }
     method codes() {
-        nqp::p6box_i(nqp::chars(nqp::unbox_s(self.Str)));
+        self.Str.codes
     }
 
     method fmt($format = '%s') {
@@ -89,20 +89,19 @@ my class Cool { # declared in BOOTSTRAP
     method substr-rw(\SELF: $from, $length?) { substr-rw(SELF,$from,$length) }
 
     method uc() {
-        nqp::p6box_s(nqp::uc(nqp::unbox_s(self.Str)))
+        self.Str.uc
     }
 
     method lc() {
-        nqp::p6box_s(nqp::lc(nqp::unbox_s(self.Str)))
+        self.Str.lc
     }
 
     method tc() {
-        my $u := nqp::unbox_s(self.Str);
-        nqp::p6box_s(nqp::uc(nqp::substr($u,0,1)) ~ nqp::substr($u,1));
+        self.Str.tc
     }
 
     method tclc() {
-        nqp::p6box_s(nqp::tclc(nqp::unbox_s(self.Str)))
+        self.Str.tclc
     }
 
     method wordcase()   { self.Str.wordcase }
@@ -125,10 +124,7 @@ my class Cool { # declared in BOOTSTRAP
     }
 
     method ord(--> Int) {
-        my $s := self.Str;
-        $s.chars
-          ?? nqp::p6box_i(nqp::ord(nqp::unbox_s($s)))
-          !! Int;
+        self.Str.ord
     }
     method chr() {
         self.Int.chr;
@@ -136,9 +132,11 @@ my class Cool { # declared in BOOTSTRAP
     method chrs(Cool:D:) {
         self>>.chr.join;
     }
+    method ords(Cool:D:) { self.Str.ords }
+
 
     method flip() {
-        nqp::p6box_s(nqp::flip(nqp::unbox_s(self.Str)))
+        self.Str.flip
     }
     method trans(*@a) { self.Str.trans(@a) }
 
@@ -222,7 +220,6 @@ my class Cool { # declared in BOOTSTRAP
         $result;
     }
 
-    method ords(Cool:D:) { self.Str.ords }
     proto method split(|) {*}
     multi method split(Regex $pat, $limit = Inf, :$all) {
         self.Stringy.split($pat, $limit, :$all);
diff --git a/src/core/Str.pm b/src/core/Str.pm
index 8a9b1ed627a..8d2898f38dd 100644
--- a/src/core/Str.pm
+++ b/src/core/Str.pm
@@ -1107,7 +1107,7 @@ my class Str does Stringy { # declared in BOOTSTRAP
 
         has str $.unsubstituted_text;
         has str $.substituted_text;
-        
+
         submethod BUILD(:$!source, :$!squash, :$!complement) { }
 
         method add_substitution($key, $value) {
@@ -1443,15 +1443,20 @@ my class Str does Stringy { # declared in BOOTSTRAP
         }).join;
     }
 
-    method codes(Str:D:) returns Int:D {
-        nqp::p6box_i(nqp::chars(nqp::unbox_s(self)))
-    }
-
     method path(Str:D:) returns IO::Path:D {
         DEPRECATED('IO', |<2014.11 2015.11>);
         IO::Path.new(self)
     }
 
+    proto method codes(|) { * }
+    multi method codes(Str:D:) returns Int:D {
+        nqp::p6box_i(nqp::chars(nqp::unbox_s(self)))
+    }
+    multi method codes(Str:U:) returns Int:D {
+        self.Str;  # generate undefined warning
+        0
+    }
+
     proto method chars(|) { * }
     multi method chars(Str:D:) returns Int:D {
         nqp::p6box_i(nqp::chars($!value))
@@ -1461,6 +1466,57 @@ my class Str does Stringy { # declared in BOOTSTRAP
         0
     }
 
+    proto method uc(|) { * }
+    multi method uc(Str:D:) {
+        nqp::p6box_s(nqp::uc($!value));
+    }
+    multi method uc(Str:U:) {
+        self.Str;
+    }
+
+    proto method lc(|) { * }
+    multi method lc(Str:D:) {
+        nqp::p6box_s(nqp::lc($!value));
+    }
+    multi method lc(Str:U:) {
+        self.Str;
+    }
+
+    proto method tc(|) { * }
+    multi method tc(Str:D:) {
+        nqp::p6box_s(nqp::uc(nqp::substr($!value,0,1)) ~ nqp::substr($!value,1));
+    }
+    multi method tc(Str:U:) {
+        self.Str
+    }
+
+    proto method tclc(|) { * }
+    multi method tclc(Str:D:) {
+        nqp::p6box_s(nqp::tclc($!value))
+    }
+    multi method tclc(Str:U:) {
+        self.Str
+    }
+
+    proto method flip(|) { * }
+    multi method flip(Str:D:) {
+        nqp::p6box_s(nqp::flip($!value))
+    }
+    multi method flip(Str:U:) {
+        self.Str
+    }
+
+    proto method ord(|) { * }
+    multi method ord(Str:D:) returns Int {
+        nqp::chars($!value)
+          ?? nqp::p6box_i(nqp::ord($!value))
+          !! Int;
+    }
+    multi method ord(Str:U:) {
+        self.Str;
+        Int
+    }
+
 }
 
 
@@ -1713,7 +1769,7 @@ multi sub substr(Str() $what, \start, $want?) {
 
 sub substr-rw(\what, \start, $want?) is rw {
     my $Str := nqp::istype(what,Str) ?? what !! what.Str;
-    
+
     # should really be int, but \ then doesn't work for rw access
     my $r := SUBSTR-SANITY($Str, start, $want, my Int $from, my Int $chars);
     $r.defined