https://bugs.freedesktop.org/show_bug.cgi?id=4117
================================================================================
--- freedesktop.org.xml.in
+++ freedesktop.org.xml.in
@@ -2184,11 +2184,13 @@
     <glob pattern="*.mrw" />
   </mime-type> 
   <mime-type type="image/x-canon-crw">
+    <sub-class-of type="image/tiff"/>
     <comment>Canon raw image</comment>
     <glob pattern="*.crw"/>
     <glob pattern="*.cr2"/>
   </mime-type>
   <mime-type type="image/x-nikon-nef">
+    <sub-class-of type="image/tiff"/>
     <comment>Nikon raw image</comment>
     <glob pattern="*.nef"/>
   </mime-type>