diff --git a/doc/build.xml b/doc/build.xml
index d8799f3..3b64647 100644
--- a/doc/build.xml
+++ b/doc/build.xml
@@ -29,14 +29,12 @@
 		<path refid="USER_SOURCE_PATH" />
 	</path>
 
-	<condition property="tools.path" value="${gwt.tools.lib}/jdk/tools-1.4.2_09.jar" else="${gwt.tools.lib}/jdk/tools-1.5.0_07.jar:${gwt.tools.lib}/jdk/tools-1.4.2_09.jar">
-		<equals arg1="${ant.java.version}" arg2="1.4"/>
-	</condition>
+	<property.ensure name="java.tools.path" location="${java.home}/../lib/tools.jar" message="Cannot find ${java.home}/../lib/tools.jar; please use a JDK when building doc rather than a JRE."/>
 
 	<path id="DOC_PATH">
 		<pathelement location="./src" />
 		<pathelement location="${gwt.build.lib}/gwt-doctool.jar" />
-		<path path="${tools.path}" />
+		<path path="${java.tools.path}" />
 		<path refid="USER_SOURCE_PATH" />
 	</path>