diff --git a/cime_config/testdefs/testmods_dirs/clm/decStart/shell_commands b/cime_config/testdefs/testmods_dirs/clm/decStart/shell_commands
index 3000705067..f3e89bb4fa 100755
--- a/cime_config/testdefs/testmods_dirs/clm/decStart/shell_commands
+++ b/cime_config/testdefs/testmods_dirs/clm/decStart/shell_commands
@@ -1,2 +1,2 @@
 ./xmlchange RUN_STARTDATE=2001-12-30
-./xmlchange CLM_BLDNML_OPTS=-ignore_warnings
+./xmlchange CLM_BLDNML_OPTS=-ignore_warnings --append