diff --git a/src/main/java/org/warp/filesponge/DiskCache.java b/src/main/java/org/warp/filesponge/DiskCache.java
index 77b325a..b097202 100644
--- a/src/main/java/org/warp/filesponge/DiskCache.java
+++ b/src/main/java/org/warp/filesponge/DiskCache.java
@@ -115,9 +115,21 @@ public class DiskCache implements URLsDiskHandler, URLsWriter {
 									@Nullable DiskMetadata result;
 									if (prevBytes != null) {
 										DiskMetadata prevMeta = diskMetadataSerializer.deserialize(prevBytes);
-										if (!prevMeta.downloadedBlocks().getBoolean(dataBlock.getId())) {
+										if (!prevMeta.isDownloadedBlock(dataBlock.getId())) {
 											BooleanArrayList bal = prevMeta.downloadedBlocks().clone();
-											bal.set(dataBlock.getId(), true);
+											if (prevMeta.size() == -1) {
+												if (bal.size() > dataBlock.getId()) {
+													bal.set(dataBlock.getId(), true);
+												} else if (bal.size() == dataBlock.getId()) {
+													bal.add(true);
+												} else {
+													throw new IndexOutOfBoundsException(
+															"Trying to write a block too much far from the last block. Previous total blocks: "
+																	+ bal.size() + " Current block id: " + dataBlock.getId());
+												}
+											} else {
+												bal.set(dataBlock.getId(), true);
+											}
 											result = new DiskMetadata(prevMeta.size(), bal);
 										} else {
 											result = prevMeta;
@@ -161,13 +173,15 @@ public class DiskCache implements URLsDiskHandler, URLsWriter {
 										try {
 											int blockOffset = getBlockOffset(blockId);
 											int blockLength = data.readableBytes();
-											if (blockOffset + blockLength >= meta.size()) {
-												if (blockOffset + blockLength > meta.size()) {
-													throw new IllegalStateException("Overflowed data size");
+											if (meta.size() != -1) {
+												if (blockOffset + blockLength >= meta.size()) {
+													if (blockOffset + blockLength > meta.size()) {
+														throw new IllegalStateException("Overflowed data size");
+													}
+												} else {
+													// Intermediate blocks must be of max size
+													assert data.readableBytes() == BLOCK_SIZE;
 												}
-											} else {
-												// Intermediate blocks must be of max size
-												assert data.readableBytes() == BLOCK_SIZE;
 											}
 											return new DataBlock(blockOffset, blockLength, data.retain());
 										} finally {
diff --git a/src/main/java/org/warp/filesponge/DiskMetadata.java b/src/main/java/org/warp/filesponge/DiskMetadata.java
index db1a21a..3ff3d95 100644
--- a/src/main/java/org/warp/filesponge/DiskMetadata.java
+++ b/src/main/java/org/warp/filesponge/DiskMetadata.java
@@ -47,9 +47,13 @@ public record DiskMetadata(int size, BooleanArrayList downloadedBlocks) {
 		return downloadedFullyVal;
 	}
 
+	@SuppressWarnings("UnusedReturnValue")
 	private int getBlocksCount() {
+		if (size == -1) {
+			return downloadedBlocks().size();
+		}
 		var expectedBlocksCount = getBlocksCount(size, FileSponge.BLOCK_SIZE);
-		if (this.downloadedBlocks.size() != expectedBlocksCount) {
+		if (this.downloadedBlocks().size() != expectedBlocksCount) {
 			throw new IllegalStateException(
 					"Blocks array length (" + this.downloadedBlocks().size() + ") != expected blocks count ("
 							+ expectedBlocksCount + ")");
@@ -58,6 +62,9 @@ public record DiskMetadata(int size, BooleanArrayList downloadedBlocks) {
 	}
 
 	public static int getBlocksCount(int size, int blockSize) {
+		if (size == -1) {
+			return 0;
+		}
 		return (size + (blockSize - size % blockSize)) / blockSize;
 	}
 
@@ -65,6 +72,14 @@ public record DiskMetadata(int size, BooleanArrayList downloadedBlocks) {
 		return new Metadata(size);
 	}
 
+	public boolean isDownloadedBlock(int id) {
+		if (size == -1 && downloadedBlocks().size() <= id) {
+			return false;
+		} else {
+			return downloadedBlocks().getBoolean(id);
+		}
+	}
+
 	public static class DiskMetadataSerializer implements Serializer<DiskMetadata, ByteBuf> {
 
 		private final ByteBufAllocator allocator;
@@ -79,7 +94,12 @@ public record DiskMetadata(int size, BooleanArrayList downloadedBlocks) {
 				var bais = new ByteBufInputStream(serialized);
 				var dis = new DataInputStream(bais);
 				int size = dis.readInt();
-				int blocksCount = getBlocksCount(size, FileSponge.BLOCK_SIZE);
+				int blocksCount;
+				if (size == -1) {
+					blocksCount = dis.readShort();
+				} else {
+					blocksCount = getBlocksCount(size, FileSponge.BLOCK_SIZE);
+				}
 				var downloadedBlocks = new BooleanArrayList(blocksCount);
 				for (int i = 0; i < blocksCount; i++) {
 					downloadedBlocks.add(dis.readBoolean());
@@ -98,8 +118,12 @@ public record DiskMetadata(int size, BooleanArrayList downloadedBlocks) {
 			try (var bos = new ByteBufOutputStream(buffer)) {
 				try (var dos = new DataOutputStream(bos)) {
 					dos.writeInt(deserialized.size());
-					deserialized.getBlocksCount();
-					for (boolean downloadedBlock : deserialized.downloadedBlocks) {
+					if (deserialized.size == -1) {
+						dos.writeShort(deserialized.getBlocksCount());
+					} else {
+						deserialized.getBlocksCount();
+					}
+					for (boolean downloadedBlock : deserialized.downloadedBlocks()) {
 						dos.writeBoolean(downloadedBlock);
 					}
 				}