diff --git a/macs2.wdl b/macs2.wdl
index f241544938be42ae051fcc523ccbb7bc1a77d743..88ae526ceb71223f41967ef45814046d764853d8 100644
--- a/macs2.wdl
+++ b/macs2.wdl
@@ -5,7 +5,7 @@ task PeakCalling {
     String sampleName
     Int? threads
     Int? memory
-    Boolean? nomodel
+    Boolean nomodel = false
 
     command {
         set -e -o pipefail