diff --git a/src/liblzma/subblock/subblock_encoder.c b/src/liblzma/subblock/subblock_encoder.c
index 0987df96..e1af4a45 100644
--- a/src/liblzma/subblock/subblock_encoder.c
+++ b/src/liblzma/subblock/subblock_encoder.c
@@ -98,7 +98,7 @@ struct lzma_coder_s {
 		bool got_input;
 
 		uint8_t *flags;
-		size_t flags_size;
+		uint32_t flags_size;
 
 		lzma_next_coder subcoder;