diff --git a/servers/avfs/lock.c b/servers/avfs/lock.c
index 8b459e91f..58eddb077 100644
--- a/servers/avfs/lock.c
+++ b/servers/avfs/lock.c
@@ -43,7 +43,8 @@ int req;			/* either F_SETLK or F_SETLKW */
   mo = f->filp_mode;
   if (ltype != F_UNLCK && ltype != F_RDLCK && ltype != F_WRLCK) return(EINVAL);
   if (req == F_GETLK && ltype == F_UNLCK) return(EINVAL);
-  if ( (f->filp_vno->v_mode & I_TYPE) != I_REGULAR) return(EINVAL);
+  if ( (f->filp_vno->v_mode & I_TYPE) != I_REGULAR &&
+	(f->filp_vno->v_mode & I_TYPE) != I_BLOCK_SPECIAL) return(EINVAL);
   if (req != F_GETLK && ltype == F_RDLCK && (mo & R_BIT) == 0) return(EBADF);
   if (req != F_GETLK && ltype == F_WRLCK && (mo & W_BIT) == 0) return(EBADF);