diff --git a/cscripts/csiactobs.py b/cscripts/csiactobs.py
index 0972e35..1bf704a 100755
--- a/cscripts/csiactobs.py
+++ b/cscripts/csiactobs.py
@@ -85,6 +85,10 @@ class csiactobs(ctools.cscript):
         # Initialise application by calling the appropriate class constructor
         self._init_cscript(argv)
 
+        # Append an observation list to XML instance
+        self._xml.append(gammalib.GXmlElement('observation_list title="observation list"'))
+        self._xml_obslist = self._xml.element('observation_list', 0)
+
         # Return
         return
 
@@ -559,12 +563,7 @@ class csiactobs(ctools.cscript):
 
         # Clear models
         self._models.clear()
-
-        # Clear XML file and append an observation list
-        self._xml.clear()
-        self._xml.append(gammalib.GXmlElement('observation_list title="observation list"'))
-        lib = self._xml.element('observation_list', 0)
-
+        
         # Log output
         msg = 'Looping over %d runs' % len(self._runlist)
         self._log_header1(gammalib.TERSE, msg)
@@ -713,7 +712,7 @@ class csiactobs(ctools.cscript):
                                                       run_emax.TeV()))
 
             # Append observation to XML and set attributes
-            obs = lib.append('observation')
+            obs = self._xml_obslist.append('observation')
             obs.attribute('name', object_name)
             obs.attribute('id', str(obs_id))
             obs.attribute('instrument', telescope)
@@ -768,7 +767,7 @@ class csiactobs(ctools.cscript):
         self._write_summary()
 
         # Write warning in no observation could be used from runlist
-        if lib.size() == 0:
+        if self._xml_obslist.size() == 0:
             self._log_string(gammalib.NORMAL, 'WARNING: No observation was '
                              'appended from specified runlist')
 
diff --git a/test/test_csiactobs.py b/test/test_csiactobs.py
index a55bfde..2a99389 100755
--- a/test/test_csiactobs.py
+++ b/test/test_csiactobs.py
@@ -148,7 +148,7 @@ class Test(test):
 
         # Check empty observation definition XML file
         self._check_obsdef('csiactobs_obs_py0.xml', 0)
-        
+
         # Check empty model definition XML file
         self._check_moddef('csiactobs_bgd_py0.xml', 0)