diff --git a/doc/conf.py b/doc/conf.py
index 35b2874..00865f9 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -83,7 +83,7 @@
 }
 
 extlinks = {'sfs': ('https://sfs.readthedocs.io/en/3.2/%s',
-                    'https://sfs.rtfd.io/')}
+                    'https://sfs.rtfd.io/%s')}
 
 plot_include_source = True
 plot_html_show_source_link = False
diff --git a/sfs/array.py b/sfs/array.py
index 1727475..148a5b5 100644
--- a/sfs/array.py
+++ b/sfs/array.py
@@ -664,7 +664,7 @@ def weights_midpoint(positions, *, closed):
     >>> x0, n0, a0 = sfs.array.circular(2**5, 1)
     >>> a = sfs.array.weights_midpoint(x0, closed=True)
     >>> max(abs(a0-a))
-    0.0003152601902411123
+    np.float64(0.0003152601902411123)
 
     """
     positions = _util.asarray_of_rows(positions)
@@ -672,7 +672,7 @@ def weights_midpoint(positions, *, closed):
         before, after = -1, 0  # cyclic
     else:
         before, after = 1, -2  # mirrored
-    positions = _np.row_stack((positions[before], positions, positions[after]))
+    positions = _np.vstack((positions[before], positions, positions[after]))
     distances = _np.linalg.norm(_np.diff(positions, axis=0), axis=1)
     return (distances[:-1] + distances[1:]) / 2