diff --git a/src/calibre/devices/kindle/driver.py b/src/calibre/devices/kindle/driver.py
index 1971faef60..ac3bcb4bc1 100644
--- a/src/calibre/devices/kindle/driver.py
+++ b/src/calibre/devices/kindle/driver.py
@@ -288,7 +288,7 @@ class KINDLE2(KINDLE):
     name           = 'Kindle 2/3/4/Touch Device Interface'
     description    = _('Communicate with the Kindle 2/3/4/Touch eBook reader.')
 
-    FORMATS        = KINDLE.FORMATS + ['pdf', 'azw4', 'pobi']
+    FORMATS        = ['azw3'] + KINDLE.FORMATS + ['pdf', 'azw4', 'pobi']
     DELETE_EXTS    = KINDLE.DELETE_EXTS + ['.mbp1', '.mbs', '.sdr']
 
     PRODUCT_ID = [0x0002, 0x0004]
@@ -449,7 +449,7 @@ class KINDLE_DX(KINDLE2):
     name           = 'Kindle DX Device Interface'
     description    = _('Communicate with the Kindle DX eBook reader.')
 
-
+    FORMATS = KINDLE2.FORMATS[1:]
     PRODUCT_ID = [0x0003]
     BCD        = [0x0100]
 
@@ -462,7 +462,6 @@ class KINDLE_FIRE(KINDLE2):
     description = _('Communicate with the Kindle Fire')
     gui_name = 'Fire'
     FORMATS = list(KINDLE2.FORMATS)
-    FORMATS.insert(0, 'azw3')
 
     PRODUCT_ID = [0x0006]
     BCD = [0x216, 0x100]
diff --git a/src/calibre/gui2/convert/mobi_output.ui b/src/calibre/gui2/convert/mobi_output.ui
index 8c1c107620..71c19fb0c4 100644
--- a/src/calibre/gui2/convert/mobi_output.ui
+++ b/src/calibre/gui2/convert/mobi_output.ui
@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>588</width>
-    <height>342</height>
+    <height>416</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -91,23 +91,33 @@
       <item row="0" column="1">
        <widget class="QComboBox" name="opt_mobi_file_type"/>
       </item>
-      <item row="1" column="0">
+      <item row="3" column="0">
        <widget class="QLabel" name="label_3">
         <property name="text">
          <string>Personal Doc tag:</string>
         </property>
        </widget>
       </item>
-      <item row="1" column="1">
+      <item row="3" column="1">
        <widget class="QLineEdit" name="opt_personal_doc"/>
       </item>
-      <item row="2" column="0" colspan="2">
+      <item row="4" column="0" colspan="2">
        <widget class="QCheckBox" name="opt_share_not_sync">
         <property name="text">
          <string>Enable sharing of book content via Facebook, etc. WARNING: Disables last read syncing</string>
         </property>
        </widget>
       </item>
+      <item row="2" column="0" colspan="2">
+       <widget class="QLabel" name="label_4">
+        <property name="text">
+         <string>&lt;b&gt;WARNING:&lt;/b&gt; Various Kindle devices have trouble displaying the new or both MOBI filetypes. If you wish to use the new format on your device, convert to AZW3 instead of MOBI.</string>
+        </property>
+        <property name="wordWrap">
+         <bool>true</bool>
+        </property>
+       </widget>
+      </item>
      </layout>
     </widget>
    </item>