diff --git a/poky/meta/classes/rootfs-postcommands.bbclass b/poky/meta/classes/rootfs-postcommands.bbclass
index e66ed59..fbfa63f 100644
--- a/poky/meta/classes/rootfs-postcommands.bbclass
+++ b/poky/meta/classes/rootfs-postcommands.bbclass
@@ -23,7 +23,7 @@
 #
 # We do this with _append because the default value might get set later with ?=
 # and we don't want to disable such a default that by setting a value here.
-APPEND_append = '${@bb.utils.contains("IMAGE_FEATURES", "read-only-rootfs", " ro", "", d)}'
+APPEND:append = '${@bb.utils.contains("IMAGE_FEATURES", "read-only-rootfs", " ro", "", d)}'
 
 # Generates test data file with data store variables expanded in json format
 ROOTFS_POSTPROCESS_COMMAND += "write_image_test_data; "