1 files changed, 9 insertions, 0 deletions

diff --git a/tmk_core/common.mk b/tmk_core/common.mk
index d71fba9bc..5bae0d762 100644
--- a/tmk_core/common.mk
+++ b/tmk_core/common.mk
@@ -97,6 +97,15 @@ ifeq ($(strip $(KEYMAP_SECTION_ENABLE)), yes)
     endif
 endif
 
+ifeq ($(MASTER),right)  
+        OPT_DEFS += -DMASTER_IS_ON_RIGHT
+else 
+        ifneq ($(MASTER),left)
+$(error MASTER does not have a valid value(left/right))
+        endif
+endif
+
+
 # Version string
 OPT_DEFS += -DVERSION=$(shell (git describe --always --dirty || echo 'unknown') 2> /dev/null)