diff --git a/classes/kernel.bbclass b/classes/kernel.bbclass
index 0109ce6..a462ab4 100644
--- a/classes/kernel.bbclass
+++ b/classes/kernel.bbclass
@@ -24,7 +24,15 @@ python __anonymous () {
     machine_kernel_pr = bb.data.getVar('MACHINE_KERNEL_PR', d, True)
 
     if machine_kernel_pr:
-       bb.data.setVar('PR', machine_kernel_pr, d)
+       # Append
+       # a) .X, if the recipe's PR is rX, or
+       # b) +${PR}, if the recipe's PR doesn't begin with r
+       pr = bb.data.getVar('PR', d, True)
+       if pr.startswith('r'):
+               suffix = '.' + pr[1:]
+       else:
+               suffix = '+' + pr
+       bb.data.setVar('PR', machine_kernel_pr + suffix, d)
 }
 
 INITRAMFS_IMAGE ?= ""
diff --git a/classes/module-base.bbclass b/classes/module-base.bbclass
index 9aaaa4e..edc0774 100644
--- a/classes/module-base.bbclass
+++ b/classes/module-base.bbclass
@@ -11,7 +11,15 @@ python __anonymous () {
     machine_kernel_pr = bb.data.getVar('MACHINE_KERNEL_PR', d, True)
 
     if machine_kernel_pr:
-       bb.data.setVar('PR', machine_kernel_pr, d)
+       # Append
+       # a) .X, if the recipe's PR is rX, or
+       # b) +${PR}, if the recipe's PR doesn't begin with r
+       pr = bb.data.getVar('PR', d, True)
+       if pr.startswith('r'):
+               suffix = '.' + pr[1:]
+       else:
+               suffix = '+' + pr
+       bb.data.setVar('PR', machine_kernel_pr + suffix, d)
 }
 
 export KERNEL_VERSION = "${@base_read_file('${STAGING_KERNEL_DIR}/kernel-abiversion')}"