diff --git a/hplip.spec b/hplip.spec
index 3966512..2c8bb05 100644
--- a/hplip.spec
+++ b/hplip.spec
@@ -255,9 +255,14 @@ rm prnt/hpcups/ErnieFilter.{cpp,h} prnt/hpijs/ernieplatform.h
 %patch32 -p1 -b .colorlaserjet-mfp-m278-m281
 
 # TypeError: 'Error' object does not support indexing (bug #1564770)
+# upstream bug: https://bugs.launchpad.net/ubuntu/+source/hplip/+bug/1718129
+# in python2 it was possible to acces Exception message by index [0].
+# in python3 this is no longer possible and it causes TypeError.
 %patch33 -p1 -b .error-print-fix
 
 # TypeError: not all arguments converted during string formatting (bug #1566938)
+# upstream bug: https://bugs.launchpad.net/ubuntu/+source/hplip/+bug/616450
+# bug caused by more arguments than argument specifiers in formatted string
 %patch34 -p1 -b .hpfax-import-error-print
 
 sed -i.duplex-constraints \