diff --git a/openbis/build/build.xml b/openbis/build/build.xml
index 31bf3dd6239143972f95ab38d3cdab60945a1a2f..86b508dd95db5880b6893a3a51a3803575024066 100644
--- a/openbis/build/build.xml
+++ b/openbis/build/build.xml
@@ -309,7 +309,11 @@
     qualified name of the module.
   -->
   <target name="compile-gwt-module">
-    <delete dir="${webapp.dist}" />
+    <delete dir="${webapp.dist}" >
+    	<fileset>
+    		<exclude name="*.jar"/>
+    	</fileset>
+  	</delete>
     <java classpath="${ecp}:${gwt.lib}/gwt-dev.jar:${gwt.user.lib}:../common/${sources}:../openbis/${sources}:${sources}" 
     	classname="com.google.gwt.dev.Compiler" fork="true">
       <jvmarg value="-Xmx1024M" />