diff --git a/Wrap/Python/ba_fitmonitor.py b/Wrap/Python/ba_fitmonitor.py
index bd9c1c01de606fb9b7eaea875aa9e4b330dc0ebd..6d049bba71d02e1b5697df6ac92dcd10535a1e56 100644
--- a/Wrap/Python/ba_fitmonitor.py
+++ b/Wrap/Python/ba_fitmonitor.py
@@ -176,6 +176,8 @@ class PlotterSpecular:
         plt.plot(sim_data.axis(0).binCenters(), sim_values, 'b')
 
         xlabel = bp.get_axes_labels(exp_data)[0]
+        xlabel2 = bp.get_axes_labels(sim_data)[0]
+        assert xlabel == xlabel2, f'Different labels: "{xlabel}" in exp vs "{xlabel2}" in sim'
         legend = ['Experiment', 'BornAgain']
         if unc_values is not None:
             legend = ['Experiment', r'Exp $\pm \sigma$', 'BornAgain']