diff --git a/Important-tips.md b/Important-tips.md
index b7da5d3..f36cf39 100644
--- a/Important-tips.md
+++ b/Important-tips.md
@@ -13,4 +13,7 @@
 * Calibre can be used to upload files created by KCC.
 * Uploading KCC output with Calibre will remove *Personal* tag from cover.
 * **Don't convert files created by KCC with Calibre!** Any conversion process will corrupt the file!
-* Don't use Calibre reader to preview files created by KCC. It can't parse them correctly.
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+* Don't use Calibre reader to preview files created by KCC. It can't parse them correctly.
+
+### Hardware:
+* If you use **Kindle Keyboard** you **must** update firmware to version 3.4. Otherwise it will not be able open MOBI files created by KCC.
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