diff --git a/tasks/phylogenetic_inference/augur/task_augur_tree.wdl b/tasks/phylogenetic_inference/augur/task_augur_tree.wdl
index be6566595..af50fb9f9 100644
--- a/tasks/phylogenetic_inference/augur/task_augur_tree.wdl
+++ b/tasks/phylogenetic_inference/augur/task_augur_tree.wdl
@@ -39,6 +39,8 @@ task augur_tree {
         MODEL="~{substitution_model}"
       fi
       echo "$MODEL" > FINAL_MODEL.txt
+    else
+      echo "" > FINAL_MODEL.txt
     fi
   >>>