diff --git a/meta-phosphor/conf/distro/include/phosphor-defaults.inc b/meta-phosphor/conf/distro/include/phosphor-defaults.inc
index eb977ad..ebd3132 100644
--- a/meta-phosphor/conf/distro/include/phosphor-defaults.inc
+++ b/meta-phosphor/conf/distro/include/phosphor-defaults.inc
@@ -1,7 +1,7 @@
-OBMC_BMC_INSTANCES ?= "0"
-OBMC_CHASSIS_INSTANCES ?= "0"
-OBMC_HOST_INSTANCES ?= "0"
-OBMC_POWER_INSTANCES ?= "0"
+OBMC_BMC_INSTANCES ??= "0"
+OBMC_CHASSIS_INSTANCES ??= "0"
+OBMC_HOST_INSTANCES ??= "0"
+OBMC_POWER_INSTANCES ??= "0"
 
 # obmc-bmc-state-manager
 #