diff --git a/src/DecoderBuffer.cxx b/src/DecoderBuffer.cxx
index 0b326a6fd..78a2ccdc6 100644
--- a/src/DecoderBuffer.cxx
+++ b/src/DecoderBuffer.cxx
@@ -70,6 +70,12 @@ decoder_buffer_free(DecoderBuffer *buffer)
 	g_free(buffer);
 }
 
+const InputStream &
+decoder_buffer_get_stream(const DecoderBuffer *buffer)
+{
+	return *buffer->is;
+}
+
 bool
 decoder_buffer_is_empty(const DecoderBuffer *buffer)
 {
diff --git a/src/DecoderBuffer.hxx b/src/DecoderBuffer.hxx
index d09416b06..0eaf0c4f3 100644
--- a/src/DecoderBuffer.hxx
+++ b/src/DecoderBuffer.hxx
@@ -52,6 +52,10 @@ decoder_buffer_new(Decoder *decoder, InputStream &is,
 void
 decoder_buffer_free(DecoderBuffer *buffer);
 
+gcc_pure
+const InputStream &
+decoder_buffer_get_stream(const DecoderBuffer *buffer);
+
 gcc_pure
 bool
 decoder_buffer_is_empty(const DecoderBuffer *buffer);