diff --git a/demo/gptools_mds_ne.py b/demo/gptools_mds_ne.py
index <HASH>..<HASH> 100644
--- a/demo/gptools_mds_ne.py
+++ b/demo/gptools_mds_ne.py
@@ -208,8 +208,8 @@ gp.add_data(R_mag_mean, 0, n=1)
 # Try block constraint:
 R_out = scipy.linspace(0.92, 0.95, 5)
 zeros_out = scipy.zeros_like(R_out)
-gp.add_data(R_out, zeros_out)
-gp.add_data(R_out, zeros_out, n=1)
+gp.add_data(R_out, zeros_out, err_y=0.001)
+gp.add_data(R_out, zeros_out, err_y=0.1, n=1)
 
 # Make constraint functions:
 def l_cf(params):
Try adding noise on the block constraints.