diff --git a/src/disk_io_thread.cpp b/src/disk_io_thread.cpp
index ea5b23988..f9f1102c7 100644
--- a/src/disk_io_thread.cpp
+++ b/src/disk_io_thread.cpp
@@ -432,6 +432,7 @@ namespace libtorrent
 		int pos = 0;
 		int start = 0;
 		int blocks_in_piece = 0;
+		int first_block = -1;
 		if (avoid_readback)
 		{
 			// with the avoid read-back mode, only consider blocks
@@ -446,7 +447,11 @@ namespace libtorrent
 
 		for (int i = 0; i < blocks_in_piece; ++i)
 		{
-			if (p.blocks[i].buf) ++current;
+			if (p.blocks[i].buf)
+			{
+				if (first_block == -1) first_block = i;
+				++current;
+			}
 			else
 			{
 				if (current > len)
@@ -464,6 +469,12 @@ namespace libtorrent
 			pos = start;
 		}
 
+		if (avoid_readback && first_block >= 0 && p.next_block_to_hash - first_block > lower_limit)
+		{
+			len = flush_range(p, first_block, p.next_block_to_hash, l);
+			return len;
+		}
+
 		if (len < lower_limit || len <= 0) return 0;
 		len = flush_range(p, pos, pos + len, l);
 		return len;