diff --git a/macs2.wdl b/macs2.wdl
index 9880c944a6b0942effc88472f64487b165d15d39..4c0125ef8eadb93883f7a589e3e726e71db8e78b 100644
--- a/macs2.wdl
+++ b/macs2.wdl
@@ -14,7 +14,7 @@ task PeakCalling {
         --treatment ${sep = ' ' bamFiles} \
         --outdir ${outDir} \
         --name ${sampleName} \
-        ${default=false true='--nomodel' false='' nomodel}
+        ${default=false true='--nomodel' nomodel}
     }
 
     output {