diff --git a/lib/HarfBuzz/Map.rakumod b/lib/HarfBuzz/Map.rakumod
index 17da8bc..f5dd5c9 100644
--- a/lib/HarfBuzz/Map.rakumod
+++ b/lib/HarfBuzz/Map.rakumod
@@ -2,7 +2,7 @@ unit class HarfBuzz::Map;
 
 use HarfBuzz::Set;
 use HarfBuzz::Raw;
-use HarfBuzz::Raw::Defs :types;
+use HarfBuzz::Raw::Defs :types, :hb-set-value;
 
 has hb_map:D $!raw handles<elems> = hb_map::create();
 method raw { $!raw }
@@ -21,12 +21,13 @@ method values {
     }
 }
 
-method exists(UInt:D $i --> Int) {
-    $!raw.exists($i).so;
+method exists(UInt:D() $k --> Int) {
+    $!raw.exists($k).so;
 }
 
-method AT-POS(UInt:D $i --> Int) {
-    $i < $.elems ?? $!raw.get($i) !! Int
+method AT-KEY(UInt:D() $k --> Int) {
+    my $v := $!raw.get($k);
+    $v == HB_SET_VALUE_INVALID ?? Int !! $v;
 }
 
 submethod DESTROY { .destroy with $!raw }
diff --git a/t/face.t b/t/face.t
index a126301..6a5d0c2 100644
--- a/t/face.t
+++ b/t/face.t
@@ -21,10 +21,12 @@ subtest 'unicode-set', {
 subtest 'unicode-to-gid-map', {
     my HarfBuzz::Map $unicode-map = $face.unicode-to-gid-map;
     ok $unicode-map.exists(42), 'exists';
+    nok $unicode-map.exists(31), '!exists';
     my HarfBuzz::Set $keys = $unicode-map.keys;
     my HarfBuzz::Set $values = $unicode-map.values;
     is $values.array[10], 11, 'values';
     is $unicode-map.elems, 854, 'elems';
-    is $unicode-map[42], 11;
+    is $unicode-map{42}, 11;
+    is-deeply $unicode-map{31}, Int;
 }