diff --git a/TODO b/TODO
index 1bd9eda0..adc5f7fc 100644
--- a/TODO
+++ b/TODO
@@ -2,7 +2,24 @@
 
 - unlink temps earlier on *nix systems
 
-- disc_thresh should default to eg. 100mb
+  the file is created by setupout, which is called just before generate or
+  writeline, so perhaps unlink on evalstart?
+
+  no, on a rewind we need to be able to close and reopen, argh
+
+- why is im_setupout() necessary for WIO output? couldn't writeline call it if
+  it's not been called?
+
+  equally, could pincheck/poutcheck/outcheck be made optional?
+  im_region_create() could call pincheck for you, for example
+
+  open_lazy does a pincheck to rewind the disc conversion, but that could be
+  removed
+
+  incheck is necessary to make ->data valid I suppose
+
+
+
 
 - lcms2 needs testing
 
diff --git a/libvips/iofuncs/im_open.c b/libvips/iofuncs/im_open.c
index 15666245..343bfa5f 100644
--- a/libvips/iofuncs/im_open.c
+++ b/libvips/iofuncs/im_open.c
@@ -311,7 +311,9 @@ disc_threshold( void )
 
 		done = TRUE;
 
-		threshold = 1024 * 1024;
+		/* 100mb default.
+		 */
+		threshold = 100 * 1024 * 1024;
 
 		if( (env = g_getenv( "IM_DISC_THRESHOLD" )) ) 
 			threshold = parse_size( env );
@@ -322,7 +324,6 @@ disc_threshold( void )
 #ifdef DEBUG
 		printf( "disc_threshold: %zd bytes\n", threshold );
 #endif /*DEBUG*/
-
 	}
 
 	return( threshold );
@@ -555,7 +556,7 @@ evalend_cb( Progress *progress )
  *       ]|
  *
  *       will copy via disc if "fred.tif" is more than 500 Mbytes
- *       uncompressed.
+ *       uncompressed. The default threshold is 100MB.
  *     </para>
  *   </listitem>
  *   <listitem>