diff --git a/defaults.xml b/defaults.xml
index af0fa8431..36cd661b0 100644
--- a/defaults.xml
+++ b/defaults.xml
@@ -17,6 +17,8 @@ Started September 2000 by David Megginson, david@megginson.com
     <!-- Limit the time we need to spend in simulation loops to 1 second -->
     <max-simtime-per-frame type="double">1.0</max-simtime-per-frame>
     <session type="int" userarchive="y">0</session>
+    <nasal-gc-threaded type="bool">true</nasal-gc-threaded>
+    <nasal-gc-threaded-wait type="bool">false</nasal-gc-threaded-wait>
     <paths>
       <screenshot-dir type="string" userarchive="y"/>
       <!-- defaults to current working dir -->