diff --git a/common/core.mk b/common/core.mk
index e5264b0..7d505c0 100644
--- a/common/core.mk
+++ b/common/core.mk
@@ -42,6 +42,9 @@
 backslash := \a
 backslash := $(patsubst %a,%,$(backslash))
 
+TOP :=$= .
+TOPDIR :=$=
+
 # Prevent accidentally changing these variables
 .KATI_READONLY := SHELL empty space comma newline pound backslash