diff --git a/ChangeLog b/ChangeLog
index acd5699a..b0b97bfa 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -20,6 +20,14 @@
 - better handling of input files in vips7 command-line interface
 - sequential can skip ahead, so extract / insert are now seq
 
+16/7/12 started 7.28.10
+- wopconst was broken
+- vips_sign() was broken
+- png save compression range was wrong
+- more/moreeq was wrong
+- vips7 ppm save with options was broken 
+- don't cache write operations
+
 18/6/12 started 7.28.9
 - slightly more memory debugging output
 - remove references to the static bicubic interpolator from the docs
diff --git a/configure.in b/configure.in
index 5397b64f..5f75bc95 100644
--- a/configure.in
+++ b/configure.in
@@ -37,7 +37,7 @@ VIPS_VERSION_STRING=$VIPS_VERSION-`date`
 #   binary interface changes not backwards compatible?: reset age to 0
 
 LIBRARY_CURRENT=33
-LIBRARY_REVISION=1
+LIBRARY_REVISION=2
 LIBRARY_AGE=1
 
 # patched into include/vips/version.h
diff --git a/libvips/arithmetic/math2.c b/libvips/arithmetic/math2.c
index 3869e9c4..b6cfe6f4 100644
--- a/libvips/arithmetic/math2.c
+++ b/libvips/arithmetic/math2.c
@@ -22,6 +22,8 @@
  * 	- im_powtra() adapated to make math2.c
  * 12/11/11
  * 	- redone as a class
+ * 17/7/12
+ * 	- wopconst was broken
  */
 
 /*
@@ -401,7 +403,7 @@ vips_math2_const_class_init( VipsMath2ConstClass *class )
 		_( "Operation" ), 
 		_( "math to perform" ),
 		VIPS_ARGUMENT_REQUIRED_INPUT,
-		G_STRUCT_OFFSET( VipsMath2, math2 ),
+		G_STRUCT_OFFSET( VipsMath2Const, math2 ),
 		VIPS_TYPE_OPERATION_MATH2, VIPS_OPERATION_MATH2_POW ); 
 }
 
diff --git a/libvips/deprecated/im_vips2ppm.c b/libvips/deprecated/im_vips2ppm.c
index 3fc21b9e..311aaf3c 100644
--- a/libvips/deprecated/im_vips2ppm.c
+++ b/libvips/deprecated/im_vips2ppm.c
@@ -66,5 +66,5 @@ im_vips2ppm( IMAGE *in, const char *filename )
 		}
 	}
 
-	return( vips_ppmsave( in, filename, "ascii", ascii, NULL ) ); 
+	return( vips_ppmsave( in, name, "ascii", ascii, NULL ) ); 
 }
diff --git a/libvips/foreign/foreign.c b/libvips/foreign/foreign.c
index 70a00150..36e0bba7 100644
--- a/libvips/foreign/foreign.c
+++ b/libvips/foreign/foreign.c
@@ -890,7 +890,7 @@ vips_foreign_load_build( VipsObject *object )
 }
 
 static VipsOperationFlags 
-vips_foreign_load_real_get_flags( VipsOperation *operation )
+vips_foreign_load_operation_get_flags( VipsOperation *operation )
 {
 	VipsForeignLoad *load = VIPS_FOREIGN_LOAD( operation );
 	VipsOperationFlags flags;
@@ -920,7 +920,7 @@ vips_foreign_load_class_init( VipsForeignLoadClass *class )
 	object_class->nickname = "fileload";
 	object_class->description = _( "file loaders" );
 
-	operation_class->get_flags = vips_foreign_load_real_get_flags;
+	operation_class->get_flags = vips_foreign_load_operation_get_flags;
 
 	VIPS_ARG_IMAGE( class, "out", 2, 
 		_( "Output" ), 
@@ -1428,6 +1428,10 @@ vips_foreign_save_class_init( VipsForeignSaveClass *class )
 	 */
 	operation_class->flags |= VIPS_OPERATION_SEQUENTIAL;
 
+	/* Must not cache savers.
+	 */
+	operation_class->flags |= VIPS_OPERATION_NOCACHE;
+
 	/* Default to no coding allowed.
 	 */
 	for( i = 0; i < VIPS_CODING_LAST; i++ )
diff --git a/libvips/foreign/pngsave.c b/libvips/foreign/pngsave.c
index 1979a7a8..53eacaac 100644
--- a/libvips/foreign/pngsave.c
+++ b/libvips/foreign/pngsave.c
@@ -2,6 +2,8 @@
  *
  * 2/12/11
  * 	- wrap a class around the png writer
+ * 16/7/12
+ * 	- compression should be 0-9, not 1-10
  */
 
 /*
@@ -104,7 +106,7 @@ vips_foreign_save_png_class_init( VipsForeignSavePngClass *class )
 		_( "Compression factor" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT,
 		G_STRUCT_OFFSET( VipsForeignSavePng, compression ),
-		1, 10, 6 );
+		0, 9, 6 );
 
 	VIPS_ARG_BOOL( class, "interlace", 7, 
 		_( "Interlace" ), 
diff --git a/libvips/include/vips/operation.h b/libvips/include/vips/operation.h
index 8689dcc2..eafa2b4c 100644
--- a/libvips/include/vips/operation.h
+++ b/libvips/include/vips/operation.h
@@ -96,8 +96,7 @@ typedef struct _VipsOperationClass {
 	 */
 	void (*usage)( struct _VipsOperationClass *, VipsBuf * );
 
-	/* Return a set of operation flags. If @get_flags is NULL, just use
-	 * flags.
+	/* Return a set of operation flags. 
 	 */
 	VipsOperationFlags (*get_flags)( VipsOperation * ); 
 	VipsOperationFlags flags;
diff --git a/libvips/iofuncs/cache.c b/libvips/iofuncs/cache.c
index 55273763..bf1c236f 100644
--- a/libvips/iofuncs/cache.c
+++ b/libvips/iofuncs/cache.c
@@ -265,9 +265,15 @@ vips_value_equal( GParamSpec *pspec, GValue *v1, GValue *v2 )
 	if( generic == G_TYPE_PARAM_DOUBLE ) 
 		return( g_value_get_double( v1 ) ==
 			g_value_get_double( v2 ) );
-	if( generic == G_TYPE_PARAM_STRING ) 
-		return( strcmp( g_value_get_string( v1 ),
-			g_value_get_string( v2 ) ) == 0 );
+	if( generic == G_TYPE_PARAM_STRING ) {
+		const char *s1 = g_value_get_string( v1 );
+		const char *s2 = g_value_get_string( v2 );
+
+		if( s1 == s2 )
+			return( TRUE );
+		else
+			return( s1 && s2 && strcmp( s1, s2 ) == 0 );
+	}
 	if( generic == G_TYPE_PARAM_BOXED ) 
 		return( g_value_get_boxed( v1 ) ==
 			g_value_get_boxed( v2 ) );
diff --git a/po/en_GB.gmo b/po/en_GB.gmo
index e69de29b..9906858d 100644
Binary files a/po/en_GB.gmo and b/po/en_GB.gmo differ