diff --git a/arch/powerpc/cpu/mpc85xx/config.mk b/arch/powerpc/cpu/mpc85xx/config.mk
index 72c964c..1470f95 100644
--- a/arch/powerpc/cpu/mpc85xx/config.mk
+++ b/arch/powerpc/cpu/mpc85xx/config.mk
@@ -5,7 +5,7 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-PLATFORM_CPPFLAGS += -Wa,-me500 -msoft-float -mno-string
+PLATFORM_CPPFLAGS += -DCONFIG_MPC85xx -Wa,-me500 -msoft-float -mno-string
 
 # -mspe=yes is needed to have -mno-spe accepted by a buggy GCC;
 # see "[PATCH,rs6000] make -mno-spe work as expected" on