diff --git a/macs2.wdl b/macs2.wdl
index 8d89f3af89dbd7f2e88798c84b840816ac832a4b..70fea707d138cda234a087e39550cef09f757654 100644
--- a/macs2.wdl
+++ b/macs2.wdl
@@ -29,7 +29,7 @@ task PeakCalling {
         String outDir = "macs2"
         String sampleName
         String format = "AUTO"
-        Boolean? nomodel
+        Boolean nomodel = false
         String? gensz
         Int? extsize
         Int? shiftsize