diff --git a/conf/machine/include/rpi-default-versions.inc b/conf/machine/include/rpi-default-versions.inc
index e65a4ae..2007cc0 100644
--- a/conf/machine/include/rpi-default-versions.inc
+++ b/conf/machine/include/rpi-default-versions.inc
@@ -1,3 +1,3 @@
 # RaspberryPi BSP default versions
 
-PREFERRED_VERSION_linux-raspberrypi ?= "4.4.%"
+PREFERRED_VERSION_linux-raspberrypi ??= "4.4.%"