diff --git a/src/liblzma/common/block_encoder.c b/src/liblzma/common/block_encoder.c
index 168846ad..520ecc5a 100644
--- a/src/liblzma/common/block_encoder.c
+++ b/src/liblzma/common/block_encoder.c
@@ -217,6 +217,7 @@ lzma_block_encoder(lzma_stream *strm, lzma_block *block)
 	lzma_next_strm_init(lzma_block_encoder_init, strm, block);
 
 	strm->internal->supported_actions[LZMA_RUN] = true;
+	strm->internal->supported_actions[LZMA_SYNC_FLUSH] = true;
 	strm->internal->supported_actions[LZMA_FINISH] = true;
 
 	return LZMA_OK;