diff --git a/src/disk_io_thread.cpp b/src/disk_io_thread.cpp
index 41dc5ee92..06b5b37fb 100644
--- a/src/disk_io_thread.cpp
+++ b/src/disk_io_thread.cpp
@@ -1145,6 +1145,9 @@ namespace libtorrent
 		// call disk function
 		int ret = (this->*(job_functions[j->action]))(j, completed_jobs);
 
+		// note that -2 erros are OK
+		TORRENT_ASSERT(ret != -1 || (j->error.ec && j->error.operation != 0));
+
 		--m_outstanding_jobs;
 
 		if (ret == retry_job)
@@ -1209,6 +1212,8 @@ namespace libtorrent
 		int ret = j->storage->get_storage_impl()->readv(&b, 1
 			, j->piece, j->d.io.offset, file_flags, j->error);
    
+		TORRENT_ASSERT(ret >= 0 || j->error.ec);
+
 		if (!j->error.ec)
 		{
 			boost::uint32_t read_time = total_microseconds(time_now_hires() - start_time);
@@ -2545,6 +2550,8 @@ namespace libtorrent
 
 		m_disk_cache.maybe_free_piece(pe);
 
+		TORRENT_ASSERT(ret >= 0 || (j->error.ec && j->error.operation != 0));
+
 		return ret < 0 ? ret : 0;
 	}
 
diff --git a/src/storage.cpp b/src/storage.cpp
index 7ea8d733e..a2037abc0 100644
--- a/src/storage.cpp
+++ b/src/storage.cpp
@@ -1224,6 +1224,9 @@ namespace libtorrent
 				bytes_transferred = (int)((*handle).*op.op)(adjusted_offset
 					, tmp_bufs, num_tmp_bufs, e, op.mode);
 
+				// we either get an error or 0 or more bytes read
+				TORRENT_ASSERT(e || bytes_transferred >= 0);
+
 #ifdef TORRENT_DISK_STATS
 				write_access_log(adjusted_offset + bytes_transferred, handle->file_id(), op_end | flags, time_now_hires());
 #endif
@@ -1235,12 +1238,20 @@ namespace libtorrent
 			{
 				ec.ec = e;
 				ec.file = file_index;
-				ec.operation = (op.mode & file::rw_mask) == file::read_only ? storage_error::read : storage_error::write;
+				ec.operation = (op.mode & file::rw_mask) == file::read_only
+					? storage_error::read : storage_error::write;
 				return -1;
 			}
 
 			if (file_bytes_left != bytes_transferred)
+			{
+				// fill in this information in case the caller wants to treat
+				// this as an error
+				ec.file = file_index;
+				ec.operation = (op.mode & file::rw_mask) == file::read_only
+					? storage_error::read : storage_error::write;
 				return bytes_transferred;
+			}
 
 			advance_bufs(current_buf, bytes_transferred);
 			TORRENT_ASSERT(count_bufs(current_buf, bytes_left - file_bytes_left) <= num_bufs);
diff --git a/src/torrent.cpp b/src/torrent.cpp
index 0a100fb48..c4bf1e68c 100644
--- a/src/torrent.cpp
+++ b/src/torrent.cpp
@@ -2527,6 +2527,8 @@ namespace libtorrent
 #endif
 				)
 			{
+				TORRENT_ASSERT(j->error.file >= 0);
+
 				// skip this file by updating m_checking_piece to the first piece following it
 				file_storage const& st = m_torrent_file->files();
 				boost::uint64_t file_size = st.file_size(j->error.file);