diff --git a/src/gwt/build.xml b/src/gwt/build.xml

index 6581bd9..36eadc1 100644

--- a/src/gwt/build.xml

+++ b/src/gwt/build.xml

@@ -26,6 +26,7 @@

    <property name="gwt.main.module" value="org.rstudio.studio.RStudio"/>

    <property name="ace.bin" value="src/org/rstudio/studio/client/workbench/views/source/editors/text/ace"/>

    <property name="json2.bin" value="www/js"/>

+   <property environment="env"/>

    <path id="project.class.path">

       <pathelement location="bin"/>

@@ -102,6 +103,7 @@

          </classpath>

          <!-- add jvmarg -Xss16M or similar if you see a StackOverflowError -->

          <jvmarg value="-Xmx512M"/>

+         <jvmarg value="-Djava.util.prefs.userRoot=${env.T}"/>

          <arg value="-war"/>

          <arg value="www"/>

          <arg value="-localWorkers"/>