diff --git a/ChangeLog b/ChangeLog
index 1db9bb66..7954265a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 12/1/16 started 8.2.2
 - changes to ease compiling C++ binding with MSVC
+- reorder file tests to put slow loaders last
+- ifthenelse needs less C stack during eval
 
 1/1/16 started 8.2.1
 - add a compat stub, thanks Benjamin
diff --git a/libvips/conversion/ifthenelse.c b/libvips/conversion/ifthenelse.c
index 0304a4fa..1170cca6 100644
--- a/libvips/conversion/ifthenelse.c
+++ b/libvips/conversion/ifthenelse.c
@@ -437,8 +437,15 @@ vips_ifthenelse_build( VipsObject *object )
 
 	/* Condition is cast to uchar, then/else to a common type.
 	 */
-	if( vips_cast( size[2], &format[2], VIPS_FORMAT_UCHAR, NULL ) )
-		return( -1 );
+	if( size[2]->BandFmt != VIPS_FORMAT_UCHAR ) { 
+		if( vips_cast( size[2], &format[2], VIPS_FORMAT_UCHAR, NULL ) )
+			return( -1 );
+	}
+	else {
+		format[2] = size[2];
+		g_object_ref( format[2] ); 
+	}
+
 	if( vips__formatalike_vec( size, format, 2 ) ) 
 		return( -1 ); 
 
diff --git a/libvips/foreign/analyzeload.c b/libvips/foreign/analyzeload.c
index 37cc68d7..0bb1c6cd 100644
--- a/libvips/foreign/analyzeload.c
+++ b/libvips/foreign/analyzeload.c
@@ -118,6 +118,10 @@ vips_foreign_load_analyze_class_init( VipsForeignLoadAnalyzeClass *class )
 
 	foreign_class->suffs = vips_foreign_analyze_suffs;
 
+	/* is_a() is not that quick ... lower the priority.
+	 */
+	foreign_class->priority = -50;
+
 	load_class->is_a = vips__isanalyze;
 	load_class->get_flags_filename = 
 		vips_foreign_load_analyze_get_flags_filename;
diff --git a/libvips/foreign/csvload.c b/libvips/foreign/csvload.c
index e51949fe..ad1b3646 100644
--- a/libvips/foreign/csvload.c
+++ b/libvips/foreign/csvload.c
@@ -125,6 +125,10 @@ vips_foreign_load_csv_class_init( VipsForeignLoadCsvClass *class )
 
 	foreign_class->suffs = vips__foreign_csv_suffs;
 
+	/* is_a() is not that quick ... lower the priority.
+	 */
+	foreign_class->priority = -50;
+
 	load_class->get_flags_filename = 
 		vips_foreign_load_csv_get_flags_filename;
 	load_class->get_flags = vips_foreign_load_csv_get_flags;
diff --git a/libvips/foreign/fitsload.c b/libvips/foreign/fitsload.c
index 678d1947..179e497c 100644
--- a/libvips/foreign/fitsload.c
+++ b/libvips/foreign/fitsload.c
@@ -109,6 +109,10 @@ vips_foreign_load_fits_class_init( VipsForeignLoadFitsClass *class )
 	object_class->nickname = "fitsload";
 	object_class->description = _( "load a FITS image" );
 
+	/* is_a() is not that quick ... lower the priority.
+	 */
+	foreign_class->priority = -50;
+
 	foreign_class->suffs = vips__fits_suffs;
 
 	load_class->is_a = vips__fits_isfits;
diff --git a/libvips/foreign/jpegload.c b/libvips/foreign/jpegload.c
index 3a5fa031..2e81077e 100644
--- a/libvips/foreign/jpegload.c
+++ b/libvips/foreign/jpegload.c
@@ -240,6 +240,10 @@ vips_foreign_load_jpeg_file_class_init( VipsForeignLoadJpegFileClass *class )
 
 	foreign_class->suffs = jpeg_suffs;
 
+	/* We are fast at is_a(), so high priority.
+	 */
+	foreign_class->priority = 200;
+
 	load_class->get_flags_filename = 
 		vips_foreign_load_jpeg_file_get_flags_filename;
 	load_class->is_a = vips_foreign_load_jpeg_file_is_a;
diff --git a/libvips/foreign/matrixload.c b/libvips/foreign/matrixload.c
index 254be289..24742d48 100644
--- a/libvips/foreign/matrixload.c
+++ b/libvips/foreign/matrixload.c
@@ -138,6 +138,10 @@ vips_foreign_load_matrix_class_init( VipsForeignLoadMatrixClass *class )
 
 	foreign_class->suffs = vips__foreign_matrix_suffs;
 
+	/* is_a() is not that quick ... lower the priority.
+	 */
+	foreign_class->priority = -50;
+
 	load_class->is_a = vips__matrix_ismatrix;
 	load_class->get_flags_filename = 
 		vips_foreign_load_matrix_get_flags_filename;
diff --git a/libvips/foreign/openexrload.c b/libvips/foreign/openexrload.c
index 94f147d7..cc0a432b 100644
--- a/libvips/foreign/openexrload.c
+++ b/libvips/foreign/openexrload.c
@@ -129,6 +129,10 @@ vips_foreign_load_openexr_class_init( VipsForeignLoadOpenexrClass *class )
 
 	foreign_class->suffs = vips_foreign_openexr_suffs;
 
+	/* We are fast at is_a(), so high priority.
+	 */
+	foreign_class->priority = 200;
+
 	load_class->is_a = vips__openexr_isexr;
 	load_class->get_flags_filename = 
 		vips_foreign_load_openexr_get_flags_filename;
diff --git a/libvips/foreign/pngload.c b/libvips/foreign/pngload.c
index bd855d65..63f5ee46 100644
--- a/libvips/foreign/pngload.c
+++ b/libvips/foreign/pngload.c
@@ -129,6 +129,10 @@ vips_foreign_load_png_class_init( VipsForeignLoadPngClass *class )
 
 	foreign_class->suffs = vips__png_suffs;
 
+	/* We are fast at is_a(), so high priority.
+	 */
+	foreign_class->priority = 200;
+
 	load_class->is_a = vips__png_ispng;
 	load_class->get_flags_filename = 
 		vips_foreign_load_png_get_flags_filename;
diff --git a/libvips/foreign/ppmload.c b/libvips/foreign/ppmload.c
index 81accecc..55a5abaf 100644
--- a/libvips/foreign/ppmload.c
+++ b/libvips/foreign/ppmload.c
@@ -118,6 +118,10 @@ vips_foreign_load_ppm_class_init( VipsForeignLoadPpmClass *class )
 
 	foreign_class->suffs = vips__ppm_suffs;
 
+	/* We are fast at is_a(), so high priority.
+	 */
+	foreign_class->priority = 200;
+
 	load_class->is_a = vips__ppm_isppm;
 	load_class->get_flags_filename = 
 		vips_foreign_load_ppm_get_flags_filename;
diff --git a/libvips/foreign/radload.c b/libvips/foreign/radload.c
index f199fc14..66ab5d55 100644
--- a/libvips/foreign/radload.c
+++ b/libvips/foreign/radload.c
@@ -121,6 +121,10 @@ vips_foreign_load_rad_class_init( VipsForeignLoadRadClass *class )
 
 	foreign_class->suffs = vips__rad_suffs;
 
+	/* is_a() is not that quick ... lower the priority.
+	 */
+	foreign_class->priority = -50;
+
 	load_class->is_a = vips__rad_israd;
 	load_class->get_flags_filename = 
 		vips_foreign_load_rad_get_flags_filename;
diff --git a/libvips/foreign/tiffload.c b/libvips/foreign/tiffload.c
index c453d1a3..853e63f0 100644
--- a/libvips/foreign/tiffload.c
+++ b/libvips/foreign/tiffload.c
@@ -179,6 +179,10 @@ vips_foreign_load_tiff_file_class_init( VipsForeignLoadTiffFileClass *class )
 	object_class->nickname = "tiffload";
 	object_class->description = _( "load tiff from file" );
 
+	/* We are fast, but must test after openslideload.
+	 */
+	foreign_class->priority = 50;
+
 	foreign_class->suffs = vips__foreign_tiff_suffs;
 
 	load_class->is_a = vips__istiff;
diff --git a/libvips/foreign/vipsload.c b/libvips/foreign/vipsload.c
index 41ac40b3..317014a3 100644
--- a/libvips/foreign/vipsload.c
+++ b/libvips/foreign/vipsload.c
@@ -123,6 +123,10 @@ vips_foreign_load_vips_class_init( VipsForeignLoadVipsClass *class )
 
 	foreign_class->suffs = vips__suffs;
 
+	/* We are fast at is_a(), so high priority.
+	 */
+	foreign_class->priority = 200;
+
 	load_class->is_a = vips_foreign_load_vips_is_a;
 	load_class->get_flags = vips_foreign_load_vips_get_flags;
 	load_class->get_flags_filename = 
diff --git a/libvips/foreign/webpload.c b/libvips/foreign/webpload.c
index 51ed3db6..cb7edcb8 100644
--- a/libvips/foreign/webpload.c
+++ b/libvips/foreign/webpload.c
@@ -229,6 +229,7 @@ vips_foreign_load_webp_buffer_class_init(
 {
 	GObjectClass *gobject_class = G_OBJECT_CLASS( class );
 	VipsObjectClass *object_class = (VipsObjectClass *) class;
+	VipsForeignClass *foreign_class = (VipsForeignClass *) class;
 	VipsForeignLoadClass *load_class = (VipsForeignLoadClass *) class;
 
 	gobject_class->set_property = vips_object_set_property;
@@ -237,6 +238,10 @@ vips_foreign_load_webp_buffer_class_init(
 	object_class->nickname = "webpload_buffer";
 	object_class->description = _( "load webp from buffer" );
 
+	/* is_a() is not that quick ... lower the priority.
+	 */
+	foreign_class->priority = -50;
+
 	load_class->is_a_buffer = vips__iswebp_buffer; 
 	load_class->header = vips_foreign_load_webp_buffer_header;
 	load_class->load = vips_foreign_load_webp_buffer_load;