diff --git a/libvips/include/vips/resample.h b/libvips/include/vips/resample.h
index 3706955d..da0b4b65 100644
--- a/libvips/include/vips/resample.h
+++ b/libvips/include/vips/resample.h
@@ -58,7 +58,7 @@ int im_match_linear_search( VipsImage *ref, VipsImage *sec, VipsImage *out,
 
 
 
-int vips_shrink( VipsImage *in, VipsImage *out, 
+int vips_shrink( VipsImage *in, VipsImage **out, 
 	double xshrink, double yshrink, ... )
 	__attribute__((sentinel));
 
diff --git a/libvips/resample/shrink.c b/libvips/resample/shrink.c
index 990c2ce4..9499c14b 100644
--- a/libvips/resample/shrink.c
+++ b/libvips/resample/shrink.c
@@ -403,7 +403,7 @@ vips_shrink_init( VipsShrink *shrink )
  * Returns: 0 on success, -1 on error
  */
 int
-vips_shrink( VipsImage *in, VipsImage *out, 
+vips_shrink( VipsImage *in, VipsImage **out, 
 	double xshrink, double yshrink, ... )
 {
 	va_list ap;