diff --git a/src/liblzma/common/info.c b/src/liblzma/common/info.c
index b05bd031..ab7fc999 100644
--- a/src/liblzma/common/info.c
+++ b/src/liblzma/common/info.c
@@ -367,7 +367,7 @@ lzma_info_metadata_set(lzma_info *info, lzma_allocator *allocator,
 		lzma_bool eat_index)
 {
 	// Validate *metadata.
-	if (!lzma_vli_is_valid(metadata->header_metadata_size)
+	if (metadata->header_metadata_size > LZMA_VLI_VALUE_MAX
 			|| !lzma_vli_is_valid(metadata->total_size)
 			|| !lzma_vli_is_valid(metadata->uncompressed_size)) {
 		if (eat_index) {
@@ -403,15 +403,10 @@ lzma_info_metadata_set(lzma_info *info, lzma_allocator *allocator,
 	}
 
 	// Size of Header Metadata
-	if (!is_header_metadata) {
-		// If it is marked unknown in Metadata, it means that
-		// it's not present.
-		const lzma_vli size = metadata->header_metadata_size
-					!= LZMA_VLI_VALUE_UNKNOWN
-				? metadata->header_metadata_size : 0;
+	if (!is_header_metadata)
 		return_if_error(lzma_info_size_set(
-				info, LZMA_INFO_HEADER_METADATA, size));
-	}
+				info, LZMA_INFO_HEADER_METADATA,
+				metadata->header_metadata_size));
 
 	// Total Size
 	if (metadata->total_size != LZMA_VLI_VALUE_UNKNOWN)
diff --git a/src/liblzma/common/metadata_decoder.c b/src/liblzma/common/metadata_decoder.c
index 5016af61..356a9e31 100644
--- a/src/liblzma/common/metadata_decoder.c
+++ b/src/liblzma/common/metadata_decoder.c
@@ -169,6 +169,12 @@ process(lzma_coder *coder, lzma_allocator *allocator)
 				return LZMA_DATA_ERROR;
 
 			--coder->todo_count;
+		} else {
+			// Zero indicates that Size of Header Metadata Block
+			// is not present. That is, after successful Metadata
+			// decoding, metadata->header_metadata_size is
+			// never LZMA_VLI_VALUE_UNKNOWN.
+			coder->metadata->header_metadata_size = 0;
 		}
 
 		coder->sequence = SEQ_TOTAL_SIZE;
diff --git a/src/liblzma/common/metadata_encoder.c b/src/liblzma/common/metadata_encoder.c
index 17587c5c..9f4a15b0 100644
--- a/src/liblzma/common/metadata_encoder.c
+++ b/src/liblzma/common/metadata_encoder.c
@@ -87,8 +87,7 @@ process(lzma_coder *coder)
 	case SEQ_FLAGS:
 		coder->buffer[coder->buffer_size] = 0;
 
-		if (coder->metadata.header_metadata_size
-				!= LZMA_VLI_VALUE_UNKNOWN)
+		if (coder->metadata.header_metadata_size != 0)
 			coder->buffer[coder->buffer_size] |= 0x01;
 
 		if (coder->metadata.total_size != LZMA_VLI_VALUE_UNKNOWN)
@@ -109,8 +108,7 @@ process(lzma_coder *coder)
 		break;
 
 	case SEQ_HEADER_METADATA_SIZE:
-		if (coder->metadata.header_metadata_size
-				!= LZMA_VLI_VALUE_UNKNOWN)
+		if (coder->metadata.header_metadata_size != 0)
 			write_vli(coder->metadata.header_metadata_size);
 
 		coder->sequence = SEQ_TOTAL_SIZE;
@@ -373,13 +371,14 @@ lzma_metadata_size(const lzma_metadata *metadata)
 	lzma_vli size = 1; // Metadata Flags
 
 	// Validate header_metadata_size, total_size, and uncompressed_size.
-	if (!lzma_vli_is_valid(metadata->header_metadata_size)
+	if (metadata->header_metadata_size > LZMA_VLI_VALUE_MAX
 			|| !lzma_vli_is_valid(metadata->total_size)
+			|| metadata->total_size == 0
 			|| !lzma_vli_is_valid(metadata->uncompressed_size))
 		return 0;
 
 	// Add the sizes of these three fields.
-	if (metadata->header_metadata_size != LZMA_VLI_VALUE_UNKNOWN)
+	if (metadata->header_metadata_size != 0)
 		size += lzma_vli_size(metadata->header_metadata_size);
 
 	if (metadata->total_size != LZMA_VLI_VALUE_UNKNOWN)
diff --git a/tests/test_info.c b/tests/test_info.c
index c073fafe..0de95431 100644
--- a/tests/test_info.c
+++ b/tests/test_info.c
@@ -527,7 +527,7 @@ test6(void)
 	// still present in Footer.
 	reset();
 	metadata = my_metadata;
-	metadata.header_metadata_size = LZMA_VLI_VALUE_UNKNOWN;
+	metadata.header_metadata_size = 0;
 	expect(lzma_info_size_set(info, LZMA_INFO_HEADER_METADATA, 0)
 			== LZMA_OK);
 	expect(lzma_info_metadata_set(info, NULL, &metadata, true, false)
@@ -539,7 +539,7 @@ test6(void)
 	// from Footer.
 	reset();
 	metadata = my_metadata;
-	metadata.header_metadata_size = LZMA_VLI_VALUE_UNKNOWN;
+	metadata.header_metadata_size = 0;
 	expect(lzma_info_metadata_set(info, NULL, &my_metadata, true, false)
 			== LZMA_OK);
 	expect(lzma_info_size_set(info, LZMA_INFO_HEADER_METADATA,