diff --git a/mailnews/base/search/resources/content/FilterListDialog.xul b/mailnews/base/search/resources/content/FilterListDialog.xul
index 5c8228bfe22..bd57473b021 100644
--- a/mailnews/base/search/resources/content/FilterListDialog.xul
+++ b/mailnews/base/search/resources/content/FilterListDialog.xul
@@ -58,7 +58,7 @@ Rights Reserved.
        rdf:containment="http://home.netscape.com/NC-rdf#child">
           <template>
           <rule>
-            <treechildren>
+            <treechildren flex="1">
             <treeitem uri="..." open="true"
                    Enabled="rdf:http://home.netscape.com/NC-rdf#Enabled">
                   <treerow >
@@ -73,8 +73,10 @@ Rights Reserved.
           </rule>
           </template>
 
-      <treecol style="width: 85%" rdf:resource="http://home.netscape.com/NC-rdf#Name" id="nameColumn"/>
-      <treecol style="width: 15%" id="activeColumn"/>
+      <treecolgroup>
+        <treecol style="width: 0px" flex="85" rdf:resource="http://home.netscape.com/NC-rdf#Name" id="nameColumn"/>
+        <treecol style="width: 0px" flex="15" id="activeColumn"/>
+      </treecolgroup>
 
       <treehead>
         <treerow>
diff --git a/xpfe/components/directory/directory.xul b/xpfe/components/directory/directory.xul
index 0c49a5cca30..eb7dc77d811 100644
--- a/xpfe/components/directory/directory.xul
+++ b/xpfe/components/directory/directory.xul
@@ -53,9 +53,10 @@
         </treechildren>
       </template>
 
-      <treecol id="FilenameColumn" rdf:resource="http://home.netscape.com/NC-rdf#Name" sortActive="true" sortDirection="ascending" />
-      <treecol id="ContentLengthColumn" rdf:resource="http://home.netscape.com/NC-rdf#Content-Length"/>
-      <treecol id="LastModColumn" rdf:resource="http://home.netscape.com/WEB-rdf#LastModifiedDate"/>
+      <treecolgroup>
+        <treecol flex="1" id="FilenameColumn" rdf:resource="http://home.netscape.com/NC-rdf#Name" sortActive="true" sortDirection="ascending" />
+        <treecol flex="1" id="ContentLengthColumn" rdf:resource="http://home.netscape.com/NC-rdf#Content-Length"/>
+        <treecol flex="1" id="LastModColumn" rdf:resource="http://home.netscape.com/WEB-rdf#LastModifiedDate"/>
 
       <treehead>
         <treerow>
@@ -70,7 +71,7 @@
 
       <!-- Create the treechildren here so we can attach event handlers
            at this level (rather than at the tree level -->
-      <treechildren onclick="OnClick(event);" onkeypress="OnClick(event);"/>
+      <treechildren flex="1" onclick="OnClick(event);" onkeypress="OnClick(event);"/>
 
   </tree>
 </window>