diff --git a/ChangeLog b/ChangeLog
index 025a87ab..b7b36598 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -5,6 +5,9 @@
 - return of vips_init(), but just for bindings
 - revised type.c to make it more binding-friendly
 
+8/9/14 started 7.40.8
+- fix configure on rhel6 [Lovell]
+
 21/8/14 started 7.40.7
 - width and height were swapped in matlab load
 - set interpretation more carefully on matlab load
@@ -12,6 +15,8 @@
 - fix memleak in VipsArray [Lovell]
 - fix memleak in webp load from buffer [Lovell]
 - fix memleak in png save to buffer [Lovell]
+- make out of order read in png and jpg a fatal error
+- add thread_shutdown() to C++ (and thereby to python)
 
 12/8/14 started 7.40.6
 - more doc fixes
diff --git a/configure.ac b/configure.ac
index 9193a866..bd861ec9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -37,9 +37,9 @@ VIPS_VERSION_STRING=$VIPS_VERSION-`date`
 #   binary interface changes backwards compatible?: increment age
 #   binary interface changes not backwards compatible?: reset age to 0
 
-LIBRARY_CURRENT=38
-LIBRARY_REVISION=5
-LIBRARY_AGE=0
+LIBRARY_CURRENT=39
+LIBRARY_REVISION=0
+LIBRARY_AGE=1
 
 # patched into include/vips/version.h
 AC_SUBST(VIPS_VERSION)
@@ -411,7 +411,7 @@ PACKAGES_USED="$PACKAGES_USED glib-2.0 libxml-2.0 gmodule-2.0 gobject-2.0"
 # after 2.28 we have a monotonic timer
 PKG_CHECK_MODULES(MONOTONIC, glib-2.0 >= 2.28,[
   AC_DEFINE(HAVE_MONOTONIC_TIME,1,[define if your glib has g_get_monotonic_time().])
-  ],[
+  ],[:
   ]
 )
 
@@ -432,7 +432,7 @@ PKG_CHECK_MODULES(THREADS, glib-2.0 >= 2.32,[
 # with 2.36 and after the type system inits itself
 PKG_CHECK_MODULES(TYPE_INIT, glib-2.0 < 2.36,[
   AC_DEFINE(NEED_TYPE_INIT,1,[define if your glib needs g_type_init().])
-  ],[
+  ],[:
   ]
 )
 
diff --git a/libvips/conversion/sequential.c b/libvips/conversion/sequential.c
index f9e392c1..5ab04cc0 100644
--- a/libvips/conversion/sequential.c
+++ b/libvips/conversion/sequential.c
@@ -71,7 +71,7 @@
 #include "pconversion.h"
 
 /* Stall threads that run ahead for up to this long, in seconds. Normally they
- * will be woken up long before this, once their data is ready. The timeout is
+ * will be woken once their data is ready and long before this. The timeout is
  * just to prevent a total crash in the case of accidental deadlock. 
  *
  * This has to be a long time: if we're trying to use all cores on a busy 
diff --git a/libvips/foreign/jpeg2vips.c b/libvips/foreign/jpeg2vips.c
index 2483de3c..666ec61c 100644
--- a/libvips/foreign/jpeg2vips.c
+++ b/libvips/foreign/jpeg2vips.c
@@ -916,7 +916,11 @@ read_jpeg_generate( VipsRegion *or,
 	/* And check that y_pos is correct. It should be, since we are inside
 	 * a vips_sequential().
 	 */
-	g_assert( r->top == jpeg->y_pos ); 
+	if( r->top != jpeg->y_pos ) {
+		vips_error( "VipsJpeg", 
+			_( "out of order read at line %d" ), jpeg->y_pos );
+		return( -1 );
+	}
 
 	/* Here for longjmp() from vips__new_error_exit().
 	 */
diff --git a/libvips/foreign/vipspng.c b/libvips/foreign/vipspng.c
index 8c107385..551a976e 100644
--- a/libvips/foreign/vipspng.c
+++ b/libvips/foreign/vipspng.c
@@ -483,7 +483,11 @@ png2vips_generate( VipsRegion *or,
 	/* And check that y_pos is correct. It should be, since we are inside
 	 * a vips_sequential().
 	 */
-	g_assert( r->top == read->y_pos ); 
+	if( r->top != read->y_pos ) {
+		vips_error( "vipspng", 
+			_( "out of order read at line %d" ), read->y_pos );
+		return( -1 );
+	}
 
 	for( y = 0; y < r->height; y++ ) {
 		png_bytep q = (png_bytep) VIPS_REGION_ADDR( or, 0, r->top + y );
diff --git a/libvipsCC/VImage.cc b/libvipsCC/VImage.cc
index 5709762d..f229d1d9 100644
--- a/libvipsCC/VImage.cc
+++ b/libvipsCC/VImage.cc
@@ -64,6 +64,11 @@ void shutdown()
 	vips_shutdown(); 
 }
 
+void thread_shutdown()
+{
+	vips_thread_shutdown(); 
+}
+
 void VImage::refblock::debug_print()
 {
 	std::list<refblock *>::iterator i;
diff --git a/libvipsCC/include/vips/VImage.h b/libvipsCC/include/vips/VImage.h
index c37deac8..cead3969 100644
--- a/libvipsCC/include/vips/VImage.h
+++ b/libvipsCC/include/vips/VImage.h
@@ -63,6 +63,7 @@ VIPS_NAMESPACE_START
 /* vips_init() and vips_shutdown as namespaced C++ functions.
  */
 bool init( const char *argv0 = "nothing" );
+void thread_shutdown( void ); 
 void shutdown( void ); 
 
 /* A VIPS callback, our name for im_callback_fn.
@@ -451,6 +452,8 @@ VIPS_NAMESPACE_END
 // Other VIPS protos we need 
 extern "C" {
 extern int im_init_world( const char *argv0 ); 
+extern int im_init_world( const char *argv0 ); 
+extern void vips_thread_shutdown( void ); 
 extern void im__print_all(); 
 extern void im_col_Lab2XYZ( 
 	float, float, float,
diff --git a/tools/vipsthumbnail.c b/tools/vipsthumbnail.c
index cb250fc2..a946bc0e 100644
--- a/tools/vipsthumbnail.c
+++ b/tools/vipsthumbnail.c
@@ -490,7 +490,7 @@ thumbnail_shrink( VipsObject *process, VipsImage *in,
 	if( vips_tilecache( in, &t[4], 
 		"tile_width", in->Xsize,
 		"tile_height", 10,
-		"max_tiles", (nlines * 2) / 10,
+		"max_tiles", 1 + (nlines * 2) / 10,
 		"access", VIPS_ACCESS_SEQUENTIAL,
 		"threaded", TRUE, 
 		NULL ) )