diff --git a/src/main/kotlin/ru/dbotthepony/kstarbound/client/gl/vertex/DirectVertexBuilder.kt b/src/main/kotlin/ru/dbotthepony/kstarbound/client/gl/vertex/DirectVertexBuilder.kt
index e7b24364..b53cd18b 100644
--- a/src/main/kotlin/ru/dbotthepony/kstarbound/client/gl/vertex/DirectVertexBuilder.kt
+++ b/src/main/kotlin/ru/dbotthepony/kstarbound/client/gl/vertex/DirectVertexBuilder.kt
@@ -5,11 +5,11 @@ import ru.dbotthepony.kstarbound.client.gl.GLAttributeList
 import ru.dbotthepony.kstarbound.client.gl.GLVertexBufferObject
 import ru.dbotthepony.kstarbound.util.ByteBufferOutputStream
 
-open class DirectVertexBuilder(
+open class DirectVertexBuilder<T : DirectVertexBuilder<T>>(
 	attributes: GLAttributeList,
 	type: VertexType,
 	val maxElements: Int,
-) : AbstractVertexBuilder<HeapVertexBuilder>(attributes, type) {
+) : AbstractVertexBuilder<DirectVertexBuilder<T>>(attributes, type) {
 	val maxIndexCount = maxElements * type.indicies.size
 	val maxVertexCount = maxElements * type.elements
 
diff --git a/src/main/kotlin/ru/dbotthepony/kstarbound/client/gl/vertex/StreamVertexBuilder.kt b/src/main/kotlin/ru/dbotthepony/kstarbound/client/gl/vertex/StreamVertexBuilder.kt
index bec45f20..a5d771d2 100644
--- a/src/main/kotlin/ru/dbotthepony/kstarbound/client/gl/vertex/StreamVertexBuilder.kt
+++ b/src/main/kotlin/ru/dbotthepony/kstarbound/client/gl/vertex/StreamVertexBuilder.kt
@@ -14,7 +14,7 @@ class StreamVertexBuilder(
 	attributes: GLAttributeList,
 	type: VertexType,
 	maxElements: Int,
-) : DirectVertexBuilder(attributes, type, maxElements), Closeable {
+) : DirectVertexBuilder<StreamVertexBuilder>(attributes, type, maxElements), Closeable {
 	private val vao = state.newVAO()
 	private val vbo = state.newVBO()
 	private val ebo = state.newEBO()