diff --git a/libvips/iofuncs/init.c b/libvips/iofuncs/init.c
index 5b6cf91b..b3e03d88 100644
--- a/libvips/iofuncs/init.c
+++ b/libvips/iofuncs/init.c
@@ -1313,13 +1313,9 @@ vips_block_untrusted_set_operation( VipsOperationClass *class, gboolean *state )
 {
 	g_assert( VIPS_IS_OPERATION_CLASS( class ) );
 
-	if( class->flags & VIPS_OPERATION_UNTRUSTED ) {
-		GTypeClass *type_class =  (GTypeClass *) class;
-		GType gtype = type_class->g_type;
-		const char *name = g_type_name( gtype );
-
-		vips_operation_block_set( name, *state );
-	}
+	if( class->flags & VIPS_OPERATION_UNTRUSTED )
+		vips_operation_block_set( G_OBJECT_CLASS_NAME( class ), 
+			*state );
 
 	return( NULL );
 }
diff --git a/libvips/iofuncs/operation.c b/libvips/iofuncs/operation.c
index 5c97e548..cffbae94 100644
--- a/libvips/iofuncs/operation.c
+++ b/libvips/iofuncs/operation.c
@@ -196,9 +196,10 @@
  * @VIPS_OPERATION_DEPRECATED means this is an old operation kept in vips for
  * compatibility only and should be hidden from users.
  *
- * @VIPS_OPERATION_UNTRUSTED means the operation depends on external libraries which have
- * not been hardened against attack. It should probably not be used on untrusted input. 
- * Use vips_operation_block_untrusted() to block all untrusted operations.
+ * @VIPS_OPERATION_UNTRUSTED means the operation depends on external libraries 
+ * which have not been hardened against attack. It should probably not be used 
+ * on untrusted input. Use vips_block_untrusted_set() to block all 
+ * untrusted operations.
  *
  * @VIPS_OPERATION_BLOCKED means the operation is prevented from executing. Use
  * vips_operation_block_set() to enable and disable groups of operations.