Index: lucene/common-build.xml
===================================================================
--- lucene/common-build.xml	(revision 1417604)
+++ lucene/common-build.xml	(working copy)
@@ -82,7 +82,11 @@
   <property name="args" value=""/>
 
   <property name="tests.seed" value="" />
+
+  <!-- This is a hack to be able to override the JVM count in DIH's tests to 1, so change the hidden -tests.jvms to override! -->
   <property name="tests.jvms" value="auto" />
+  <property name="-tests.jvms" value="${tests.jvms}" />
+
   <property name="tests.multiplier" value="1" />
   <property name="tests.codec" value="random" />
   <property name="tests.postingsformat" value="random" />
@@ -1160,7 +1164,7 @@
        jars so we just order it after compile-test to ensure that -->
   <target name="test" depends="clover,compile-test,install-junit4-taskdef,validate" description="Runs unit tests">
     <mkdir dir="${junit.output.dir}"/>
-    <test-macro threadNum="${tests.jvms}" />
+    <test-macro threadNum="${-tests.jvms}" />
   </target>
 
   <!--
Index: solr/contrib/dataimporthandler/build.xml
===================================================================
--- solr/contrib/dataimporthandler/build.xml	(revision 1417604)
+++ solr/contrib/dataimporthandler/build.xml	(working copy)
@@ -24,7 +24,7 @@
   </description>
 
   <!-- the tests have some parallel problems: writability to single copy of dataimport.properties -->
-  <property name="tests.jvms" value="1"/>
+  <property name="-tests.jvms" value="1"/>
 
   <import file="../contrib-build.xml"/>