diff --git a/src/calibre/gui2/convert/epub_output.ui b/src/calibre/gui2/convert/epub_output.ui
index e763acb458..75ad4b7c08 100644
--- a/src/calibre/gui2/convert/epub_output.ui
+++ b/src/calibre/gui2/convert/epub_output.ui
@@ -33,6 +33,9 @@
    </item>
    <item row="5" column="1">
     <widget class="QSpinBox" name="opt_flow_size">
+     <property name="specialValueText">
+      <string>Disabled</string>
+     </property>
      <property name="suffix">
       <string> KB</string>
      </property>