diff --git a/TODO b/TODO
index edc4b583..3b17676d 100644
--- a/TODO
+++ b/TODO
@@ -1,11 +1,13 @@
 
 - python:
 
-	- try
+	- draw_circle() etc. should copy() the image before writing, and
+	  return the copy
 
-		python test_arithmetic.py -v TestArithmetic.test_histfind
+	  accidental segvs are too easy otherwise :( 
 
-	  segv
+	  draw.c should declare arg as VIPS_ARGUMENT_REQUIRED_INPUT_OUTPUT 
+	  maybe?
 
 	- could import like this:
 
diff --git a/libvips/arithmetic/hough_circle.c b/libvips/arithmetic/hough_circle.c
index f084c5e1..620345e1 100644
--- a/libvips/arithmetic/hough_circle.c
+++ b/libvips/arithmetic/hough_circle.c
@@ -262,7 +262,7 @@ vips_hough_circle_class_init( VipsHoughClass *class )
 static void
 vips_hough_circle_init( VipsHoughCircle *hough_circle )
 {
-	hough_circle->scale = 3; 
+	hough_circle->scale = 1; 
 	hough_circle->min_radius = 10; 
 	hough_circle->max_radius = 20; 
 }
diff --git a/python/test_arithmetic.py b/python/test_arithmetic.py
index f79ebb37..77dc3059 100755
--- a/python/test_arithmetic.py
+++ b/python/test_arithmetic.py
@@ -342,5 +342,21 @@ class TestArithmetic(unittest.TestCase):
                 self.assertAlmostEqualObjects(hist.getpoint(0,0), [0])
                 self.assertAlmostEqualObjects(hist.getpoint(1,0), [50000])
 
+    def test_histfind_ndim(self):
+        im = Vips.Image.black(100, 100) + [1, 2, 3]
+
+        for fmt in noncomplex_formats:
+            hist = im.cast(fmt).hist_find_ndim()
+
+            self.assertAlmostEqualObjects(hist.getpoint(0,0)[0], 10000)
+            self.assertAlmostEqualObjects(hist.getpoint(5,5)[5], 0)
+
+            hist = im.cast(fmt).hist_find_ndim(bins = 1)
+
+            self.assertAlmostEqualObjects(hist.getpoint(0,0)[0], 10000)
+            self.assertEqual(hist.width, 1)
+            self.assertEqual(hist.height, 1)
+            self.assertEqual(hist.bands, 1)
+
 if __name__ == '__main__':
     unittest.main()