misc.go    | 6 ++++++
 torrent.go | 1 +

diff --git a/misc.go b/misc.go
index 6b589e2490c0606fc8283aa781a44729bc1f01c8..7e8b70fb9c220fa8f02ec917593cd756d7133636 100644
--- a/misc.go
+++ b/misc.go
@@ -125,6 +125,7 @@ 	for _, miFile := range upvertedSingleFileInfoFiles(md) {
 		fileName := filepath.Join(append([]string{location, md.Name}, miFile.Path...)...)
 		err = os.MkdirAll(filepath.Dir(fileName), 0777)
 		if err != nil {
+			err = fmt.Errorf("error creating data directory %q: %s", filepath.Dir(fileName), err)
 			return
 		}
 		var file *os.File
@@ -145,9 +146,14 @@ 				if err != nil {
 					return
 				}
 			}
+			if miFile.Length == 0 {
+				// Can't mmap() regions with length 0.
+				return
+			}
 			var mMap gommap.MMap
 			mMap, err = gommap.MapRegion(file.Fd(), 0, miFile.Length, gommap.PROT_READ|gommap.PROT_WRITE, gommap.MAP_SHARED)
 			if err != nil {
+				err = fmt.Errorf("error mapping file %q, length %d: %s", file.Name(), miFile.Length, err)
 				return
 			}
 			if int64(len(mMap)) != miFile.Length {
diff --git a/torrent.go b/torrent.go
index a4c002d42620b46d07815eb3dcc89ec0f13ec963..5d13d6a91326bb3cd3d53e8b4852dea21f40e01f 100644
--- a/torrent.go
+++ b/torrent.go
@@ -206,6 +206,7 @@ 	t.MetaData = infoBytes
 	t.metadataHave = nil
 	t.Data, err = mmapTorrentData(&md, dataDir)
 	if err != nil {
+		err = fmt.Errorf("error mmap'ing torrent data: %s", err)
 		return
 	}
 	t.length = t.Data.Size()