diff --git a/bag_unpacker/src/main/scala/weco/storage_service/bag_unpacker/storage/Unarchiver.scala b/bag_unpacker/src/main/scala/weco/storage_service/bag_unpacker/storage/Unarchiver.scala
index 27d008087..ec9899d1d 100644
--- a/bag_unpacker/src/main/scala/weco/storage_service/bag_unpacker/storage/Unarchiver.scala
+++ b/bag_unpacker/src/main/scala/weco/storage_service/bag_unpacker/storage/Unarchiver.scala
@@ -51,7 +51,7 @@ object Unarchiver {
     } yield iterator
 
   private def createIterator(
-    archiveInputStream: ArchiveInputStream
+    archiveInputStream: ArchiveInputStream[ArchiveEntry]
   ): Iterator[(ArchiveEntry, InputStream)] =
     new Iterator[(ArchiveEntry, InputStream)] {
       private var latest: ArchiveEntry = _
@@ -92,7 +92,7 @@ object Unarchiver {
 
   private def extract(
     inputStream: InputStream
-  ): Either[UnarchiverError, ArchiveInputStream] =
+  ): Either[UnarchiverError, ArchiveInputStream[ArchiveEntry]] =
     Try {
       // We have to wrap in a BufferedInputStream because this method
       // only takes InputStreams that support the `mark()` method.
diff --git a/bag_unpacker/src/test/scala/weco/storage_service/bag_unpacker/fixtures/CompressFixture.scala b/bag_unpacker/src/test/scala/weco/storage_service/bag_unpacker/fixtures/CompressFixture.scala
index fe83e74ae..9060d6ba1 100644
--- a/bag_unpacker/src/test/scala/weco/storage_service/bag_unpacker/fixtures/CompressFixture.scala
+++ b/bag_unpacker/src/test/scala/weco/storage_service/bag_unpacker/fixtures/CompressFixture.scala
@@ -182,7 +182,7 @@ trait CompressFixture[BagLocation <: Location, Namespace]
       compressorName: String
     )(
       outputStream: OutputStream
-    ): CompressorOutputStream = {
+    ): CompressorOutputStream[BufferedOutputStream] = {
 
       val compressorStreamFactory =
         new CompressorStreamFactory()
@@ -195,13 +195,13 @@ trait CompressFixture[BagLocation <: Location, Namespace]
           compressorName,
           bufferedOutputStream
         )
-    }
+    }.asInstanceOf[CompressorOutputStream[BufferedOutputStream]]
 
     private def packer(
       archiverName: String
     )(
       outputStream: OutputStream
-    ): ArchiveOutputStream = {
+    ): ArchiveOutputStream[ArchiveEntry] = {
 
       val archiveStreamFactory =
         new ArchiveStreamFactory()