gistfile1.txt

diff --git a/lib/NativeCall.pm6 b/lib/NativeCall.pm6
index b82be7b..bd4812e 100644
--- a/lib/NativeCall.pm6
+++ b/lib/NativeCall.pm6
@@ -339,9 +339,9 @@ role ExplicitlyManagedString {
     has $.cstr is rw;
 }

-multi explicitly-manage(Str $x, :$encoding = 'utf8') is export(:DEFAULT,
+multi explicitly-manage(Str $x is rw, :$encoding = 'utf8') is export(:DEFAULT,
 :utils) {
-    $x does ExplicitlyManagedString;
+    $x = $x but ExplicitlyManagedString;
     my $class = class CStr is repr('CStr') { method encoding() { $encoding; } };
     $x.cstr = nqp::box_s(nqp::unbox_s($x), nqp::decont($class));
 }