diff --git a/Sources/Common/DecodingHuffmanTree.swift b/Sources/Common/DecodingHuffmanTree.swift
index 155213cb..7345d399 100644
--- a/Sources/Common/DecodingHuffmanTree.swift
+++ b/Sources/Common/DecodingHuffmanTree.swift
@@ -6,7 +6,7 @@
 import Foundation
 import BitByteData
 
-class DecodingHuffmanTree {
+final class DecodingHuffmanTree {
 
     private let bitReader: BitReader
 
diff --git a/Sources/Common/EncodingHuffmanTree.swift b/Sources/Common/EncodingHuffmanTree.swift
index d45c6830..9fd522c7 100644
--- a/Sources/Common/EncodingHuffmanTree.swift
+++ b/Sources/Common/EncodingHuffmanTree.swift
@@ -6,7 +6,7 @@
 import Foundation
 import BitByteData
 
-class EncodingHuffmanTree {
+final class EncodingHuffmanTree {
 
     private let bitWriter: BitWriter