--- maven2-plugins/maven-assembly-plugin/src/main/java/org/apache/maven/plugin/assembly/utils/PropertyUtils.java.sav	2010-11-28 16:02:34.000000000 +0100
+++ maven2-plugins/maven-assembly-plugin/src/main/java/org/apache/maven/plugin/assembly/utils/PropertyUtils.java	2010-11-28 16:06:17.000000000 +0100
@@ -83,7 +83,12 @@
         for ( Enumeration n = props.propertyNames(); n.hasMoreElements(); )
         {
             String key = (String) n.nextElement();
-            String value = interpolator.interpolate( props.getProperty( key ), "__properties" );
+            String value = null;
+            try {
+                value = interpolator.interpolate( props.getProperty( key ), "__properties" );
+            } catch(Exception e) {
+                throw new IOException( "cannot interpolate property: " + e.getMessage(), e );
+            }
             
             props.setProperty( key, value );
         }