diff --git a/src/peer_connection.cpp b/src/peer_connection.cpp
index 05a38a84f..4025310b5 100644
--- a/src/peer_connection.cpp
+++ b/src/peer_connection.cpp
@@ -2909,9 +2909,10 @@ namespace libtorrent
 
 		TORRENT_ASSERT(!m_disconnecting);
 		TORRENT_ASSERT(t->valid_metadata());
-		TORRENT_ASSERT(block.piece_index >= 0);
+
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(int(block.piece_index) < t->torrent_file().num_pieces());
-		TORRENT_ASSERT(block.block_index >= 0);
 		TORRENT_ASSERT(int(block.block_index) < t->torrent_file().piece_size(block.piece_index));
 		TORRENT_ASSERT(!t->picker().is_requested(block) || (t->picker().num_peers(block) > 0));
 		TORRENT_ASSERT(!t->have_piece(block.piece_index));
@@ -3048,9 +3049,9 @@ namespace libtorrent
 
 		TORRENT_ASSERT(t->valid_metadata());
 
-		TORRENT_ASSERT(block.piece_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(int(block.piece_index) < t->torrent_file().num_pieces());
-		TORRENT_ASSERT(block.block_index >= 0);
 		TORRENT_ASSERT(int(block.block_index) < t->torrent_file().piece_size(block.piece_index));
 
 		// if all the peers that requested this block has been
diff --git a/src/piece_picker.cpp b/src/piece_picker.cpp
index 8718fec71..cfcc3e6e7 100644
--- a/src/piece_picker.cpp
+++ b/src/piece_picker.cpp
@@ -2046,8 +2046,8 @@ namespace libtorrent
 
 	bool piece_picker::is_requested(piece_block block) const
 	{
-		TORRENT_ASSERT(block.piece_index >= 0);
-		TORRENT_ASSERT(block.block_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(block.piece_index < m_piece_map.size());
 
 		if (m_piece_map[block.piece_index].downloading == 0) return false;
@@ -2060,8 +2060,8 @@ namespace libtorrent
 
 	bool piece_picker::is_downloaded(piece_block block) const
 	{
-		TORRENT_ASSERT(block.piece_index >= 0);
-		TORRENT_ASSERT(block.block_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(block.piece_index < m_piece_map.size());
 
 		if (m_piece_map[block.piece_index].index == piece_pos::we_have_index) return true;
@@ -2075,8 +2075,8 @@ namespace libtorrent
 
 	bool piece_picker::is_finished(piece_block block) const
 	{
-		TORRENT_ASSERT(block.piece_index >= 0);
-		TORRENT_ASSERT(block.block_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(block.piece_index < m_piece_map.size());
 
 		if (m_piece_map[block.piece_index].index == piece_pos::we_have_index) return true;
@@ -2092,8 +2092,8 @@ namespace libtorrent
 	{
 		TORRENT_ASSERT(peer == 0 || static_cast<policy::peer*>(peer)->in_use);
 		TORRENT_ASSERT(state != piece_picker::none);
-		TORRENT_ASSERT(block.piece_index >= 0);
-		TORRENT_ASSERT(block.block_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(block.piece_index < m_piece_map.size());
 		TORRENT_ASSERT(int(block.block_index) < blocks_in_piece(block.piece_index));
 		TORRENT_ASSERT(!m_piece_map[block.piece_index].have());
@@ -2150,8 +2150,8 @@ namespace libtorrent
 
 	int piece_picker::num_peers(piece_block block) const
 	{
-		TORRENT_ASSERT(block.piece_index >= 0);
-		TORRENT_ASSERT(block.block_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(block.piece_index < m_piece_map.size());
 		TORRENT_ASSERT(int(block.block_index) < blocks_in_piece(block.piece_index));
 
@@ -2186,8 +2186,8 @@ namespace libtorrent
 
 		TORRENT_ASSERT(peer == 0 || static_cast<policy::peer*>(peer)->in_use);
 
-		TORRENT_ASSERT(block.piece_index >= 0);
-		TORRENT_ASSERT(block.block_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(block.piece_index < m_piece_map.size());
 		TORRENT_ASSERT(int(block.block_index) < blocks_in_piece(block.piece_index));
 
@@ -2389,7 +2389,7 @@ namespace libtorrent
 
 		if (i == m_downloads.end()) return 0;
 
-		TORRENT_ASSERT(block.block_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
 
 		TORRENT_ASSERT(i->info[block.block_index].piece_index == block.piece_index);
 		if (i->info[block.block_index].state == block_info::state_none)
@@ -2410,8 +2410,8 @@ namespace libtorrent
 
 		TORRENT_ASSERT(peer == 0 || static_cast<policy::peer*>(peer)->in_use);
 
-		TORRENT_ASSERT(block.piece_index >= 0);
-		TORRENT_ASSERT(block.block_index >= 0);
+		TORRENT_ASSERT(block.block_index != piece_block::invalid.block_index);
+		TORRENT_ASSERT(block.piece_index != piece_block::invalid.piece_index);
 		TORRENT_ASSERT(block.piece_index < m_piece_map.size());
 		TORRENT_ASSERT(int(block.block_index) < blocks_in_piece(block.piece_index));