diff --git a/library/socket_select.c b/library/socket_select.c
index 6979a1f..d5eda1f 100644
--- a/library/socket_select.c
+++ b/library/socket_select.c
@@ -1,5 +1,5 @@
 /*
- * $Id: socket_select.c,v 1.12 2005-08-15 10:17:47 obarthel Exp $
+ * $Id: socket_select.c,v 1.13 2005-08-15 10:43:54 obarthel Exp $
  *
  * :ts=4
  *
@@ -331,6 +331,14 @@ map_descriptor_sets(
 						SHOWMSG("file is unusable; we cannot examine the file.");
 						continue;
 					}
+
+					/* If we can't make assumptions about the file position, then
+					   this better be a pipe. */
+					if(FLAG_IS_CLEAR(fd->fd_Flags,FDF_CACHE_POSITION) && fib->fib_DirEntryType != ST_PIPEFILE)
+					{
+						SHOWMSG("file is unusable; it is not a file system and not a pipe.");
+						continue;
+					}
 				}
 
 				if(file_fds != NULL && file_fd < num_file_fds)