diff --git a/attributes-kt/src/commonMain/kotlin/space/kscience/attributes/Attributes.kt b/attributes-kt/src/commonMain/kotlin/space/kscience/attributes/Attributes.kt
index ad53049eb..8ddb0cbc7 100644
--- a/attributes-kt/src/commonMain/kotlin/space/kscience/attributes/Attributes.kt
+++ b/attributes-kt/src/commonMain/kotlin/space/kscience/attributes/Attributes.kt
@@ -30,14 +30,14 @@ public interface Attributes {
     override fun hashCode(): Int
 
     public companion object {
-        public val EMPTY: Attributes = AttributesImpl(emptyMap())
+        public val EMPTY: Attributes = MapAttributes(emptyMap())
 
         public fun equals(a1: Attributes, a2: Attributes): Boolean =
             a1.keys == a2.keys && a1.keys.all { a1[it] == a2[it] }
     }
 }
 
-internal class AttributesImpl(override val content: Map<out Attribute<*>, Any?>) : Attributes {
+internal class MapAttributes(override val content: Map<out Attribute<*>, Any?>) : Attributes {
     override fun toString(): String = "Attributes(value=${content.entries})"
     override fun equals(other: Any?): Boolean = other is Attributes && Attributes.equals(this, other)
     override fun hashCode(): Int = content.hashCode()
@@ -75,7 +75,7 @@ public inline fun <reified A : FlagAttribute> Attributes.hasFlag(): Boolean =
 public fun <T, A : Attribute<T>> Attributes.withAttribute(
     attribute: A,
     attrValue: T,
-): Attributes = AttributesImpl(content + (attribute to attrValue))
+): Attributes = MapAttributes(content + (attribute to attrValue))
 
 public fun <A : Attribute<Unit>> Attributes.withAttribute(attribute: A): Attributes =
     withAttribute(attribute, Unit)
@@ -83,7 +83,7 @@ public fun <A : Attribute<Unit>> Attributes.withAttribute(attribute: A): Attribu
 /**
  * Create a new [Attributes] by modifying the current one
  */
-public fun <T> Attributes.modified(block: AttributesBuilder<T>.() -> Unit): Attributes = Attributes<T> {
+public fun <O> Attributes.modified(block: AttributesBuilder<O>.() -> Unit): Attributes = Attributes<O> {
     putAll(this@modified)
     block()
 }
@@ -91,7 +91,7 @@ public fun <T> Attributes.modified(block: AttributesBuilder<T>.() -> Unit): Attr
 /**
  * Create new [Attributes] by removing [attribute] key
  */
-public fun Attributes.withoutAttribute(attribute: Attribute<*>): Attributes = AttributesImpl(content.minus(attribute))
+public fun Attributes.withoutAttribute(attribute: Attribute<*>): Attributes = MapAttributes(content.minus(attribute))
 
 /**
  * Add an element to a [SetAttribute]
@@ -101,7 +101,7 @@ public fun <T, A : SetAttribute<T>> Attributes.withAttributeElement(
     attrValue: T,
 ): Attributes {
     val currentSet: Set<T> = get(attribute) ?: emptySet()
-    return AttributesImpl(
+    return MapAttributes(
         content + (attribute to (currentSet + attrValue))
     )
 }
@@ -114,7 +114,7 @@ public fun <T, A : SetAttribute<T>> Attributes.withoutAttributeElement(
     attrValue: T,
 ): Attributes {
     val currentSet: Set<T> = get(attribute) ?: emptySet()
-    return AttributesImpl(content + (attribute to (currentSet - attrValue)))
+    return MapAttributes(content + (attribute to (currentSet - attrValue)))
 }
 
 /**
@@ -123,13 +123,13 @@ public fun <T, A : SetAttribute<T>> Attributes.withoutAttributeElement(
 public fun <T, A : Attribute<T>> Attributes(
     attribute: A,
     attrValue: T,
-): Attributes = AttributesImpl(mapOf(attribute to attrValue))
+): Attributes = MapAttributes(mapOf(attribute to attrValue))
 
 /**
  * Create Attributes with a single [Unit] valued attribute
  */
 public fun <A : Attribute<Unit>> Attributes(
     attribute: A,
-): Attributes = AttributesImpl(mapOf(attribute to Unit))
+): Attributes = MapAttributes(mapOf(attribute to Unit))
 
-public operator fun Attributes.plus(other: Attributes): Attributes = AttributesImpl(content + other.content)
\ No newline at end of file
+public operator fun Attributes.plus(other: Attributes): Attributes = MapAttributes(content + other.content)
\ No newline at end of file
diff --git a/attributes-kt/src/commonMain/kotlin/space/kscience/attributes/AttributesBuilder.kt b/attributes-kt/src/commonMain/kotlin/space/kscience/attributes/AttributesBuilder.kt
index 0a185f74c..6f42d1dcf 100644
--- a/attributes-kt/src/commonMain/kotlin/space/kscience/attributes/AttributesBuilder.kt
+++ b/attributes-kt/src/commonMain/kotlin/space/kscience/attributes/AttributesBuilder.kt
@@ -6,13 +6,14 @@
 package space.kscience.attributes
 
 /**
- * A safe builder for [Attributes]
+ * A builder for [Attributes].
+ * The builder is not thread safe
  *
  * @param O type marker of an owner object, for which these attributes are made
  */
-public class AttributesBuilder<out O> internal constructor(
-    private val map: MutableMap<Attribute<*>, Any?>,
-) : Attributes {
+public class AttributesBuilder<out O> internal constructor() : Attributes {
+
+    private val map = mutableMapOf<Attribute<*>, Any?>()
 
     override fun toString(): String = "Attributes(value=${content.entries})"
     override fun equals(other: Any?): Boolean = other is Attributes && Attributes.equals(this, other)
@@ -56,7 +57,7 @@ public class AttributesBuilder<out O> internal constructor(
         map[this] = currentSet - attrValue
     }
 
-    public fun build(): Attributes = AttributesImpl(map)
+    public fun build(): Attributes = MapAttributes(map)
 }
 
 /**
@@ -64,4 +65,4 @@ public class AttributesBuilder<out O> internal constructor(
  * @param O the type for which attributes are built. The type is used only during compilation phase for static extension dispatch
  */
 public fun <O> Attributes(builder: AttributesBuilder<O>.() -> Unit): Attributes =
-    AttributesBuilder<O>(mutableMapOf()).apply(builder).build()
\ No newline at end of file
+    AttributesBuilder<O>().apply(builder).build()
\ No newline at end of file