Index: src/java/org/apache/fop/tools/anttasks/Fop.java
===================================================================
--- src/java/org/apache/fop/tools/anttasks/Fop.java	(revision 936376)
+++ src/java/org/apache/fop/tools/anttasks/Fop.java	(working copy)
@@ -444,6 +444,7 @@
 
     private static final String[][] EXTENSIONS = {
         {MimeConstants.MIME_FOP_AREA_TREE,   ".at.xml"},
+        {MimeConstants.MIME_FOP_IF,   ".if.xml"},
         {MimeConstants.MIME_FOP_AWT_PREVIEW, null},
         {MimeConstants.MIME_FOP_PRINT,       null},
         {MimeConstants.MIME_PDF,             ".pdf"},