diff --git a/zabbix-agent-scripts/get_nc_quota_metrics.py b/zabbix-agent-scripts/get_nc_quota_metrics.py
index ed06bb5..59124ac 100644
--- a/zabbix-agent-scripts/get_nc_quota_metrics.py
+++ b/zabbix-agent-scripts/get_nc_quota_metrics.py
@@ -47,17 +47,19 @@
                  names=column_names
                 )
 
-## In some cases assigned_quota get the value of -2 or 'none'. In these cases, we are replacing with 0
-df["assigned_quota"] = df.assigned_quota.str.replace('none','0').str.replace('-2','0')
+## In some cases assigned_quota get the value of -2 or 'none'. In these cases, we are replacing with 0.
+## If the field is not of type string don't do anything.
+if df.assigned_quota.dtype.name == 'object':
+    df["assigned_quota"] = df.assigned_quota.str.replace('none','0').str.replace('-2','0')
 
-# See https://github.com/nextcloud/user_usage_report/issues/200
-def trf_to_nr(elem):
-	if 'GB' in elem:
-		return int(elem.split()[0])*1024*1024*1024
-	else:
-		return int(elem)
+    # See https://github.com/nextcloud/user_usage_report/issues/200
+    def trf_to_nr(elem):
+    	if 'GB' in elem:
+    		return int(elem.split()[0])*1024*1024*1024
+    	else:
+    		return int(elem)
 
-df["assigned_quota"] = df.assigned_quota.apply(trf_to_nr)
+    df["assigned_quota"] = df.assigned_quota.apply(trf_to_nr)
 
 ## Transformation to int is necessary as json library cannot serialize numpy
 ## data types