diff --git a/libvips/include/vips/type.h b/libvips/include/vips/type.h
index d8c0e2c8..e5f14e56 100644
--- a/libvips/include/vips/type.h
+++ b/libvips/include/vips/type.h
@@ -148,8 +148,9 @@ typedef struct _VipsBlob {
 	VipsArea area;
 } VipsBlob;
 
-VipsBlob *vips_blob_new( VipsCallbackFn free_fn, void *data, size_t size );
-void *vips_blob_get( VipsBlob *blob, size_t *size );
+VipsBlob *vips_blob_new( VipsCallbackFn free_fn, 
+	const void *data, size_t size );
+const void *vips_blob_get( VipsBlob *blob, size_t *size );
 GType vips_blob_get_type( void );
 
 /**
diff --git a/libvips/iofuncs/type.c b/libvips/iofuncs/type.c
index f89d6a00..9d0a4a65 100644
--- a/libvips/iofuncs/type.c
+++ b/libvips/iofuncs/type.c
@@ -529,11 +529,11 @@ vips_ref_string_get_type( void )
  * Returns: (transfer full): the new #VipsBlob.
  */
 VipsBlob *
-vips_blob_new( VipsCallbackFn free_fn, void *data, size_t size )
+vips_blob_new( VipsCallbackFn free_fn, const void *data, size_t size )
 {
 	VipsArea *area;
 
-	area = vips_area_new( free_fn, data );
+	area = vips_area_new( free_fn, (void *) data );
 	area->length = size;
 
 	return( (VipsBlob *) area );
@@ -550,7 +550,7 @@ vips_blob_new( VipsCallbackFn free_fn, void *data, size_t size )
  *
  * Returns: (array length=size) (element-type guint8) (transfer none): the data
  */
-void *
+const void *
 vips_blob_get( VipsBlob *blob, size_t *size )
 {
 	return( vips_area_get_data( VIPS_AREA( blob ), 
diff --git a/python/vips8/vips.py b/python/vips8/vips.py
index 33a89fe0..3c15f399 100644
--- a/python/vips8/vips.py
+++ b/python/vips8/vips.py
@@ -83,8 +83,8 @@ class Argument:
         # turn VipsBlobs into strings 
         # FIXME ... this will involve a copy, we should use
         # buffer() instead
-        if isinstance(value, Vips.Blob):
-            value = value.get()
+#        if isinstance(value, Vips.Blob):
+#            value = value.get()
 
         return value