diff --git a/src/compression/flac.cpp b/src/compression/flac.cpp
index f56cf4bd..e854fbe6 100644
--- a/src/compression/flac.cpp
+++ b/src/compression/flac.cpp
@@ -301,8 +301,7 @@ class flac_block_compressor final : public block_compressor::impl {
       std::string hdrbuf;
       CompactSerializer::serialize(hdr, &hdrbuf);
 
-      compressed.resize(pos + hdrbuf.size());
-      ::memcpy(compressed.data() + pos, hdrbuf.data(), hdrbuf.size());
+      compressed.append(hdrbuf.data(), hdrbuf.size());
     }
 
     dwarfs_flac_stream_encoder encoder(compressed);