diff --git a/vfs_unix.go b/vfs_unix.go
index 3d1e9cf..0d8c709 100644
--- a/vfs_unix.go
+++ b/vfs_unix.go
@@ -79,7 +79,7 @@ func (l *vfsFileLocker) readLock(start, len int64) xErrorCode {
 		Type:  syscall.F_RDLCK,
 		Start: start,
 		Len:   len,
-	}), IOERR_LOCK)
+	}), IOERR_RDLOCK)
 }
 
 func (l *vfsFileLocker) writeLock(start, len int64) xErrorCode {
diff --git a/vfs_windows.go b/vfs_windows.go
index e2b72bf..e0d073f 100644
--- a/vfs_windows.go
+++ b/vfs_windows.go
@@ -94,7 +94,7 @@ func (l *vfsFileLocker) readLock(start, len uint32) xErrorCode {
 	return l.errorCode(windows.LockFileEx(windows.Handle(l.file.Fd()),
 		windows.LOCKFILE_FAIL_IMMEDIATELY,
 		0, len, 0, &windows.Overlapped{Offset: start}),
-		IOERR_LOCK)
+		IOERR_RDLOCK)
 }
 
 func (l *vfsFileLocker) writeLock(start, len uint32) xErrorCode {