diff --git a/include/libtorrent/storage.hpp b/include/libtorrent/storage.hpp
index 6ef03491a..5fe69926d 100644
--- a/include/libtorrent/storage.hpp
+++ b/include/libtorrent/storage.hpp
@@ -173,7 +173,7 @@ namespace libtorrent
 
 		error_code const& error() const { return m_error; }
 		std::string const& error_file() const { return m_error_file; }
-		void clear_error() { m_error = error_code(); m_error_file.resize(0); }
+		virtual void clear_error() { m_error = error_code(); m_error_file.resize(0); }
 
 		mutable error_code m_error;
 		mutable std::string m_error_file;
diff --git a/src/disk_io_thread.cpp b/src/disk_io_thread.cpp
index 1e510e3fe..2a37f6ab7 100644
--- a/src/disk_io_thread.cpp
+++ b/src/disk_io_thread.cpp
@@ -684,18 +684,18 @@ namespace libtorrent
 				l.unlock();
 				if (iov)
 				{
-					p.storage->write_impl(iov, p.piece, (std::min)(
+					int ret = p.storage->write_impl(iov, p.piece, (std::min)(
 						i * m_block_size, piece_size) - buffer_size, iov_counter);
 					iov_counter = 0;
-					++num_write_calls;
+					if (ret > 0) ++num_write_calls;
 				}
 				else
 				{
 					TORRENT_ASSERT(buf);
 					file::iovec_t b = { buf.get(), buffer_size };
-					p.storage->write_impl(&b, p.piece, (std::min)(
+					int ret = p.storage->write_impl(&b, p.piece, (std::min)(
 						i * m_block_size, piece_size) - buffer_size, 1);
-					++num_write_calls;
+					if (ret > 0) ++num_write_calls;
 				}
 				l.lock();
 				++m_cache_stats.writes;