diff --git a/ChangeLog b/ChangeLog
index 6e55d75d..616a33c9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,6 @@
+30/6/14 started 7.40.3
+- fix interlaced thumbnails in vipsthumbnail, thanks lovell
+
 25/6/14 started 7.40.2
 - dzsave write to zip stops at 4gb, thanks bgilbert
 - improve short option name handling, thanks bgilbert
diff --git a/configure.ac b/configure.ac
index c108e010..6921a4ae 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,7 +2,7 @@
 
 # also update the version number in the m4 macros below
 
-AC_INIT([vips], [7.40.2], [vipsip@jiscmail.ac.uk])
+AC_INIT([vips], [7.40.3], [vipsip@jiscmail.ac.uk])
 # required for gobject-introspection
 AC_PREREQ(2.62)
 
@@ -18,7 +18,7 @@ AC_CONFIG_MACRO_DIR([m4])
 # user-visible library versioning
 m4_define([vips_major_version], [7])
 m4_define([vips_minor_version], [40])
-m4_define([vips_micro_version], [2])
+m4_define([vips_micro_version], [3])
 m4_define([vips_version],
           [vips_major_version.vips_minor_version.vips_micro_version])
 
@@ -38,7 +38,7 @@ VIPS_VERSION_STRING=$VIPS_VERSION-`date`
 #   binary interface changes not backwards compatible?: reset age to 0
 
 LIBRARY_CURRENT=38
-LIBRARY_REVISION=0
+LIBRARY_REVISION=1
 LIBRARY_AGE=0
 
 # patched into include/vips/version.h
diff --git a/tools/vipsthumbnail.c b/tools/vipsthumbnail.c
index c242942c..ab411e7d 100644
--- a/tools/vipsthumbnail.c
+++ b/tools/vipsthumbnail.c
@@ -49,6 +49,8 @@
  * 7/3/14
  * 	- remove the embedded thumbnail reader, embedded thumbnails are too
  * 	  unlike the main image wrt. rotation / colour / etc.
+ * 30/6/14
+ * 	- fix interlaced thumbnail output, thanks lovell
  */
 
 #ifdef HAVE_CONFIG_H
@@ -585,8 +587,10 @@ thumbnail_rotate( VipsObject *process, VipsImage *im )
  * (eg.) "/poop/tn_somefile.jpg".
  */
 static int
-thumbnail_write( VipsImage *im, const char *filename )
+thumbnail_write( VipsObject *process, VipsImage *im, const char *filename )
 {
+	VipsImage **t = (VipsImage **) vips_object_local_array( process, 1 );
+
 	char *file;
 	char *p;
 	char buf[FILENAME_MAX];
@@ -618,7 +622,16 @@ thumbnail_write( VipsImage *im, const char *filename )
 
 	g_free( file );
 
-	if( vips_image_write_to_file( im, output_name, NULL ) ) {
+	/* We need to cache the whole of the thumbnail before we write it 
+	 * in case we are writing an interlaced image. Interlaced png (for
+	 * example) will make 7 passes over the image during write.
+	 */
+	if( vips_tilecache( im, &t[0], 
+		"threaded", TRUE,
+		"persistent", TRUE,
+		"max_tiles", -1,
+		NULL ) ||
+		vips_image_write_to_file( t[0], output_name, NULL ) ) {
 		g_free( output_name );
 		return( -1 );
 	}
@@ -644,7 +657,7 @@ thumbnail_process( VipsObject *process, const char *filename )
 			thumbnail_shrink( process, in, interp, sharpen )) ||
 		!(crop = thumbnail_crop( process, thumbnail )) ||
 		!(rotate = thumbnail_rotate( process, crop )) ||
-		thumbnail_write( rotate, filename ) )
+		thumbnail_write( process, rotate, filename ) )
 		return( -1 );
 
 	return( 0 );