diff --git a/grc/hamnet70_demod_sc16qam.grc b/grc/hamnet70_demod_sc16qam.grc
index 2169736..963163f 100644
--- a/grc/hamnet70_demod_sc16qam.grc
+++ b/grc/hamnet70_demod_sc16qam.grc
@@ -2335,7 +2335,7 @@
     </param>
     <param>
       <key>optional</key>
-      <value>False</value>
+      <value>True</value>
     </param>
     <param>
       <key>vlen</key>