diff --git a/tasks/phylogenetic_inference/augur/task_augur_tree.wdl b/tasks/phylogenetic_inference/augur/task_augur_tree.wdl
index af50fb9f9..22bd469e7 100644
--- a/tasks/phylogenetic_inference/augur/task_augur_tree.wdl
+++ b/tasks/phylogenetic_inference/augur/task_augur_tree.wdl
@@ -47,7 +47,7 @@ task augur_tree {
   output {
     File aligned_tree  = "~{build_name}_~{method}.nwk"
     String augur_version = read_string("VERSION")
-    String? iqtree_model_used = read_string("FINAL_MODEL.txt")
+    String iqtree_model_used = read_string("FINAL_MODEL.txt")
   }
   runtime {
     docker: docker
diff --git a/workflows/phylogenetics/wf_augur.wdl b/workflows/phylogenetics/wf_augur.wdl
index e77c20fb5..3a6b64ba9 100644
--- a/workflows/phylogenetics/wf_augur.wdl
+++ b/workflows/phylogenetics/wf_augur.wdl
@@ -203,7 +203,7 @@ workflow augur {
     File? auspice_input_json = augur_export.auspice_json
     File? time_tree = augur_refine.refined_tree
     File distance_tree = augur_tree.aligned_tree
-    String? iqtree_model_used = augur_tree.iqtree_model_used
+    String iqtree_model_used = augur_tree.iqtree_model_used
     File aligned_fastas = select_first([augur_align.aligned_fasta, alignment_fasta])
     File combined_assemblies = filter_sequences_by_length.filtered_fasta
     File? metadata_merged = tsv_join.out_tsv