diff --git a/pysqm/plot.py b/pysqm/plot.py
index 355753d4e3e86f1fadc1b92d81f4a3c96163d093..c45e2e4ccea3b8a79afa437dd6bbcb14cb2b86b5 100644
--- a/pysqm/plot.py
+++ b/pysqm/plot.py
@@ -452,7 +452,7 @@ class Plot(object):
          'Sky Brightness ('+config._device_shorttype+'_'+\
          config._observatory_name+')\n',fontsize='x-large')
         self.thegraph_sunalt.set_xlabel('Solar altitude (deg)',fontsize='large')
-        self.thegraph_sunalt.set_ylabel('Sky Brightness (mag/$\mathregular{arcsec^2}$)',fontsize='medium')
+        self.thegraph_sunalt.set_ylabel(r'Sky Brightness (mag/$\mathregular{arcsec^2}$)',fontsize='medium')
 
         # Auxiliary plot (Temperature)
         '''
@@ -495,7 +495,7 @@ class Plot(object):
         #self.thegraph_time.set_title('Sky Brightness (SQM-'+config._observatory_name+')',\
         # fontsize='x-large')
         self.thegraph_time.set_xlabel('Time (UTC'+UTC_offset_label+')',fontsize='large')
-        self.thegraph_time.set_ylabel('Sky Brightness (mag/$\mathregular{arcsec^2}$)',fontsize='medium')
+        self.thegraph_time.set_ylabel(r'Sky Brightness (mag/$\mathregular{arcsec^2}$)',fontsize='medium')
 
         # Auxiliary plot (Temperature)
         '''