diff --git a/webservice/webservice.py b/webservice/webservice.py
index b3a7917e616b8ce889058c66ec54b57cfa9d0f9e..256947fd240f478057886c537713c90dcb161476 100644
--- a/webservice/webservice.py
+++ b/webservice/webservice.py
@@ -1163,9 +1163,8 @@ class ActionsServer:
             self, run_nrs, rid, detectors, action, instrument, cycle, proposal,
             request_time
     ) -> (str, Optional[str]):
-        report = ""
-        ret = ""
-        delim = ", "
+        report = []
+        ret = []
         # run xfel_calibrate
         for karabo_id, dconfig in detectors.items():
             detector = dconfig['detector-type']
@@ -1183,17 +1182,15 @@ class ActionsServer:
 
             cmd = parse_config(cmd, dconfig)
             # TODO: Add detector info in returned run action status.
-            ret += (
-                await run_action(
-                    self.job_db, cmd, self.mode,
-                    proposal, run_nrs[-1], rid
-                ) + delim
-            )
+            ret.append(await run_action(
+                self.job_db, cmd, self.mode,
+                proposal, run_nrs[-1], rid
+            ))
             if '--report-to' in cmd[:-1]:
                 report_idx = cmd.index('--report-to') + 1
-                report += cmd[report_idx] + '.pdf' + delim
+                report.append(cmd[report_idx] + '.pdf')
         # return string without a tailing comma.
-        return ret[:-2], report[:-2] if report != delim else None
+        return ", ".join(ret), ", ".join(report) if len(report)!=0 else None
 
 parser = argparse.ArgumentParser(
     description='Start the calibration webservice')