diff --git a/scripts/lib/CIME/test_scheduler.py b/scripts/lib/CIME/test_scheduler.py
index 9ab9184be57..7de420c615f 100644
--- a/scripts/lib/CIME/test_scheduler.py
+++ b/scripts/lib/CIME/test_scheduler.py
@@ -585,7 +585,7 @@ def _run_catch_exceptions(self, test, phase, run):
         except (SystemExit, Exception) as e:
             exc_tb = sys.exc_info()[2]
             errput = "Test '%s' failed in phase '%s' with exception '%s'\n" % (test, phase, str(e))
-            errput += traceback.format_tb(exc_tb)
+            errput += ''.join(traceback.format_tb(exc_tb))
             self._log_output(test, errput)
             return False, errput