diff --git a/devices/e1000e/Kbuild.in b/devices/e1000e/Kbuild.in
index 8b9a03a5..889f3ac6 100644
--- a/devices/e1000e/Kbuild.in
+++ b/devices/e1000e/Kbuild.in
@@ -72,7 +72,7 @@ ifeq (@ENABLE_E1000E@,1)
 	CFLAGS_netdev-@KERNEL_E1000E@-ethercat.o = -DREV=$(REV)
 
 	ifeq (@ENABLE_DRIVER_RESOURCE_VERIFYING@,1)
-		ccflags-y := -DEC_ENABLE_DRIVER_RESOURCE_VERIFYING
+		ccflags-y += -DEC_ENABLE_DRIVER_RESOURCE_VERIFYING
 	endif
 endif