diff --git a/Adobe-error-codes.md b/Adobe-error-codes.md
index 2371b21..4a897d8 100644
--- a/Adobe-error-codes.md
+++ b/Adobe-error-codes.md
@@ -176,6 +176,10 @@ If you're an end user, make sure the internet connection on your device works pr
 
 If you are the distributor, perform the usual checks on your webserver. Check if the media URL is set correctly, check if the webserver has read access, and restart the webserver if there's still issues. 
 
+### E_ADEPT_INTERNAL
+
+Unknown internal error. Try redownloading the book again, if that doesn't help, de-authorize ADE and authorize it again.
+
 ### E_ADEPT_INVALID_FULFILLMENT_ITEM
 
 Currently there's no information about this error. If you do receive this error with the Calibre plugin, please open a bug report.