diff --git a/testmods_dirs/allactive/defaultio/shell_commands b/testmods_dirs/allactive/defaultio/shell_commands
new file mode 100755
index 0000000..94f46ab
--- /dev/null
+++ b/testmods_dirs/allactive/defaultio/shell_commands
@@ -0,0 +1,2 @@
+# Since we're doing a daily mass balance time step in CISM, we can't use the default GLC_AVG_PERIOD of yearly
+./xmlchange GLC_AVG_PERIOD=glc_coupling_period