diff --git a/NEWS b/NEWS
index e3a3ef73..55448f41 100644
--- a/NEWS
+++ b/NEWS
@@ -30,6 +30,7 @@ NEWS ( CHANGELOG and HISTORY )                                     HTMLPurifier
 ! XHTML 1.1 mode now sort-of works without any fatal errors, and
   lang is now moved over to xml:lang.
 ! Attribute transformation smoketest available at smoketests/attrTransform.php
+! Transformation of font's size attribute now handles super-large numbers
 - Possibly fatal bug with __autoload() fixed in module manager
 - Invert HTMLModuleManager->addModule() processing order to check
   prefixes first and then the literal module
diff --git a/library/HTMLPurifier/TagTransform/Font.php b/library/HTMLPurifier/TagTransform/Font.php
index ae6d7838..dedaf8b2 100644
--- a/library/HTMLPurifier/TagTransform/Font.php
+++ b/library/HTMLPurifier/TagTransform/Font.php
@@ -20,6 +20,7 @@ class HTMLPurifier_TagTransform_Font extends HTMLPurifier_TagTransform
     var $transform_to = 'span';
     
     var $_size_lookup = array(
+        '0' => 'xx-small',
         '1' => 'xx-small',
         '2' => 'small',
         '3' => 'medium',
@@ -28,9 +29,10 @@ class HTMLPurifier_TagTransform_Font extends HTMLPurifier_TagTransform
         '6' => 'xx-large',
         '7' => '300%',
         '-1' => 'smaller',
-        '+1' => 'larger',
         '-2' => '60%',
+        '+1' => 'larger',
         '+2' => '150%',
+        '+3' => '200%',
         '+4' => '300%'
     );
     
@@ -58,6 +60,15 @@ class HTMLPurifier_TagTransform_Font extends HTMLPurifier_TagTransform
         
         // handle size transform
         if (isset($attr['size'])) {
+            // normalize large numbers
+            if ($attr['size']{0} == '+' || $attr['size']{0} == '-') {
+                $size = (int) $attr['size'];
+                if ($size < -2) $attr['size'] = '-2';
+                if ($size > 4)  $attr['size'] = '+4';
+            } else {
+                $size = (int) $attr['size'];
+                if ($size > 7) $attr['size'] = '7';
+            }
             if (isset($this->_size_lookup[$attr['size']])) {
                 $prepend_style .= 'font-size:' .
                   $this->_size_lookup[$attr['size']] . ';';
diff --git a/smoketests/attrTransform.xml b/smoketests/attrTransform.xml
index 966d11a4..12dbe52e 100644
--- a/smoketests/attrTransform.xml
+++ b/smoketests/attrTransform.xml
@@ -10,7 +10,8 @@
         <sample><![CDATA[<font face="Arial">Arial</font>]]></sample>
     </group>
     <group title="font.size">
-        <sample><![CDATA[<font size="-99">-99</font>]]></sample>
+        <sample><![CDATA[<font size="-2">-2</font>]]></sample>
+        <sample><![CDATA[<font size="-1">-1</font>]]></sample>
         <sample><![CDATA[<font size="0">0</font>]]></sample>
         <sample><![CDATA[<font size="1">1</font>]]></sample>
         <sample><![CDATA[<font size="2">2</font>]]></sample>
@@ -20,7 +21,11 @@
         <sample><![CDATA[<font size="6">6</font>]]></sample>
         <sample><![CDATA[<font size="7">7</font>]]></sample>
         <sample><![CDATA[<font size="8">8</font>]]></sample>
-        <sample><![CDATA[<font size="99">99</font>]]></sample>
+        <sample><![CDATA[<font size="+1">+1</font>]]></sample>
+        <sample><![CDATA[<font size="+2">+2</font>]]></sample>
+        <sample><![CDATA[<font size="+3">+3</font>]]></sample>
+        <sample><![CDATA[<font size="+4">+4</font>]]></sample>
+        <sample><![CDATA[<font size="+5">+5</font>]]></sample>
     </group>
     <group title="center">
         <sample><![CDATA[<center>Centered</center>]]></sample>