diff -Nru casper-1.455/debian/changelog casper-1.455ubuntu1/debian/changelog
--- casper-1.455/debian/changelog	2020-10-16 16:51:20.000000000 +0000
+++ casper-1.455ubuntu1/debian/changelog	2020-11-23 18:36:27.000000000 +0000
@@ -1,3 +1,9 @@
+casper (1.455ubuntu1) hirsute; urgency=medium
+
+  * Support kernels with "+" in the version string (LP: #1905357).
+
+ -- Andrea Righi <andrea.righi@canonical.com>  Mon, 23 Nov 2020 18:36:27 +0000
+
 casper (1.455) groovy; urgency=medium
 
   * Use a tmpfs in tests; overlay is not compatible with zfs.
diff -Nru casper-1.455/debian/tests/boot casper-1.455ubuntu1/debian/tests/boot
--- casper-1.455/debian/tests/boot	2020-10-16 16:48:54.000000000 +0000
+++ casper-1.455ubuntu1/debian/tests/boot	2020-11-23 18:36:21.000000000 +0000
@@ -29,7 +29,7 @@
 
 basecmdline="boot=casper console=ttyS0"
 
-kvers="$(dpkg -l linux-image-generic | awk '/^ii/ { print $3 }' | sed -e 's/\.[0-9]\+$//; s/\.\([0-9]\+\)$/-\1/')"-generic
+kvers="$(dpkg -l linux-image-generic | awk '/^ii/ { print $3 }' | sed -e 's/+.*//; s/\.[0-9]\+$//; s/\.\([0-9]\+\)$/-\1/')"-generic
 kernel=$(echo /boot/vmlinu*-"$kvers")
 
 mkinitramfs -o casper-initrd "$kvers"