diff --git a/components/esp8266/Makefile.projbuild b/components/esp8266/Makefile.projbuild
index d90d587b..06498487 100644
--- a/components/esp8266/Makefile.projbuild
+++ b/components/esp8266/Makefile.projbuild
@@ -91,8 +91,13 @@ OTA2_BIN := ./build/$(PROJECT_NAME).app2.bin
 
 OTA_V2_TO_V3_BIN  := ./build/$(PROJECT_NAME).v2_to_v3.ota.bin
 
-CONFIG_APP2_OFFSET ?= $(CONFIG_APP1_OFFSET)
-CONFIG_APP2_SIZE ?= $(CONFIG_APP1_SIZE)
+ifndef CONFIG_APP2_OFFSET
+CONFIG_APP2_OFFSET := $(CONFIG_APP1_OFFSET)
+endif
+
+ifndef CONFIG_APP2_SIZE
+CONFIG_APP2_SIZE := $(CONFIG_APP1_SIZE)
+endif
 
 OTA1_OFFSET := $(CONFIG_APP1_OFFSET)
 ifdef CONFIG_ESP8266_BOOT_COPY_APP