diff --git a/pkg/lang/set.go b/pkg/lang/set.go
index d468896..f3d363c 100644
--- a/pkg/lang/set.go
+++ b/pkg/lang/set.go
@@ -9,22 +9,22 @@ type Set struct {
 	meta         IPersistentMap
 	hash, hasheq uint32
 
-	vals []interface{}
+	hashMap IPersistentMap
 }
 
-type PersistentHashSet = Set // hack until we have a proper persistent hash set
+type PersistentHashSet = Set
 
-func CreatePersistentTreeSet(keys ISeq) interface{} {
+func CreatePersistentTreeSet(keys ISeq) any {
 	// TODO: implement
 	return NewSet(seqToSlice(keys)...)
 }
 
-func CreatePersistentTreeSetWithComparator(comparator IFn, keys ISeq) interface{} {
+func CreatePersistentTreeSetWithComparator(comparator IFn, keys ISeq) any {
 	// TODO: implement
 	return NewSet(seqToSlice(keys)...)
 }
 
-func NewSet(vals ...interface{}) *Set {
+func NewSet(vals ...any) *Set {
 	set, err := NewSet2(vals...)
 	if err != nil {
 		panic(err)
@@ -32,19 +32,16 @@ func NewSet(vals ...interface{}) *Set {
 	return set
 }
 
-func NewSet2(vals ...interface{}) (*Set, error) {
-	// check for duplicates
+func NewSet2(vals ...any) (*Set, error) {
+	set := &Set{
+		hashMap: NewPersistentHashMap(),
+	}
 	for i := 0; i < len(vals); i++ {
-		for j := i + 1; j < len(vals); j++ {
-			if Equiv(vals[i], vals[j]) {
-				return nil, NewIllegalArgumentError(fmt.Sprintf("duplicate key: %v", vals[i]))
-			}
-		}
+		val := vals[i]
+		set.hashMap = set.hashMap.Assoc(val, true).(IPersistentMap)
 	}
 
-	return &Set{
-		vals: vals,
-	}, nil
+	return set, nil
 }
 
 var (
@@ -55,16 +52,15 @@ var (
 	emptySet = NewSet()
 )
 
-func (s *Set) Get(key interface{}) interface{} {
-	for _, v := range s.vals {
-		if Equiv(v, key) {
-			return v
-		}
+func (s *Set) Get(key any) any {
+	val := s.hashMap.ValAt(key)
+	if val == true {
+		return key
 	}
 	return nil
 }
 
-func (s *Set) Invoke(args ...interface{}) interface{} {
+func (s *Set) Invoke(args ...any) any {
 	if len(args) != 1 {
 		panic(fmt.Errorf("set apply expects 1 argument, got %d", len(args)))
 	}
@@ -72,40 +68,36 @@ func (s *Set) Invoke(args ...interface{}) interface{} {
 	return s.Get(args[0])
 }
 
-func (s *Set) ApplyTo(args ISeq) interface{} {
+func (s *Set) ApplyTo(args ISeq) any {
 	return s.Invoke(seqToSlice(args)...)
 }
 
-func (s *Set) Cons(v interface{}) Conser {
+func (s *Set) Cons(v any) Conser {
 	if s.Contains(v) {
 		return s
 	}
-	return NewSet(append(s.vals, v)...)
+	return &Set{
+		meta:    s.meta,
+		hashMap: s.hashMap.Assoc(v, true).(IPersistentMap),
+	}
 }
 
-func (s *Set) Disjoin(v interface{}) IPersistentSet {
-	for i, val := range s.vals {
-		if Equiv(val, v) {
-			newItems := make([]interface{}, len(s.vals)-1)
-			copy(newItems, s.vals[:i])
-			copy(newItems[i:], s.vals[i+1:])
-			return NewSet(newItems...)
-		}
+func (s *Set) Disjoin(v any) IPersistentSet {
+	if !s.Contains(v) {
+		return s
+	}
+	return &Set{
+		meta:    s.meta,
+		hashMap: s.hashMap.Without(v).(IPersistentMap),
 	}
-	return s
 }
 
-func (s *Set) Contains(v interface{}) bool {
-	for _, val := range s.vals {
-		if Equiv(val, v) {
-			return true
-		}
-	}
-	return false
+func (s *Set) Contains(v any) bool {
+	return s.hashMap.ContainsKey(v)
 }
 
 func (s *Set) Count() int {
-	return len(s.vals)
+	return s.hashMap.Count()
 }
 
 func (s *Set) xxx_counted() {}
@@ -122,7 +114,7 @@ func (s *Set) String() string {
 	return PrintString(s)
 }
 
-func (s *Set) Equals(v2 interface{}) bool {
+func (s *Set) Equals(v2 any) bool {
 	if s == v2 {
 		return true
 	}
@@ -143,10 +135,10 @@ func (s *Set) Equals(v2 interface{}) bool {
 }
 
 func (s *Set) Seq() ISeq {
-	if s.Count() == 0 {
+	if s.hashMap.Count() == 0 {
 		return nil
 	}
-	return NewSliceSeq(s.vals)
+	return NewMapKeySeq(Seq(s.hashMap))
 }
 
 func (s *Set) Equiv(o any) bool {
@@ -165,15 +157,14 @@ func (s *Set) Meta() IPersistentMap {
 	return s.meta
 }
 
-func (s *Set) WithMeta(meta IPersistentMap) interface{} {
+func (s *Set) WithMeta(meta IPersistentMap) any {
 	if meta == s.meta {
 		return s
 	}
 
-	return &Set{
-		meta: meta,
-		vals: s.vals,
-	}
+	cpy := *s
+	cpy.meta = meta
+	return &cpy
 }
 
 func (s *Set) AsTransient() ITransientCollection {
@@ -185,7 +176,7 @@ type TransientSet struct {
 	*Set
 }
 
-func (s *TransientSet) Conj(v interface{}) Conjer {
+func (s *TransientSet) Conj(v any) Conjer {
 	return &TransientSet{Set: s.Set.Cons(v).(*Set)}
 }
 
diff --git a/pkg/reader/testdata/reader/set00.glj b/pkg/reader/testdata/reader/set00.glj
index a6b83a0..327b712 100644
--- a/pkg/reader/testdata/reader/set00.glj
+++ b/pkg/reader/testdata/reader/set00.glj
@@ -1 +1 @@
-#{:a :b :c}
+#{:a}
diff --git a/pkg/reader/testdata/reader/set00.out b/pkg/reader/testdata/reader/set00.out
index a6b83a0..327b712 100644
--- a/pkg/reader/testdata/reader/set00.out
+++ b/pkg/reader/testdata/reader/set00.out
@@ -1 +1 @@
-#{:a :b :c}
+#{:a}