diff --git a/keyboards/lets_split/keymaps/i2c/config.h b/keyboards/lets_split/keymaps/i2c/config.h
index 332c990fc5..013542731e 100644
--- a/keyboards/lets_split/keymaps/i2c/config.h
+++ b/keyboards/lets_split/keymaps/i2c/config.h
@@ -16,8 +16,9 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 #define USE_I2C
 
-#define I2C_MASTER_LEFT
-// #define I2C_MASTER_RIGHT
+#define MASTER_LEFT
+// #define _MASTER_RIGHT
+// #define EE_HANDS
 
 #ifdef SUBPROJECT_rev1
     #include "../../rev1/config.h"
@@ -27,4 +28,4 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #endif
 #ifdef SUBPROJECT_rev2fliphalf
 	#include "../../rev2fliphalf/config.h"
-#endif
\ No newline at end of file
+#endif
diff --git a/keyboards/lets_split/keymaps/serial/config.h b/keyboards/lets_split/keymaps/serial/config.h
index 753f422dd8..ba271d1ac6 100644
--- a/keyboards/lets_split/keymaps/serial/config.h
+++ b/keyboards/lets_split/keymaps/serial/config.h
@@ -18,6 +18,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #define USE_SERIAL
 
+#define MASTER_LEFT
+// #define _MASTER_RIGHT
 // #define EE_HANDS
 
 
diff --git a/keyboards/lets_split/readme.md b/keyboards/lets_split/readme.md
index 0e903065e2..ecce3f4152 100644
--- a/keyboards/lets_split/readme.md
+++ b/keyboards/lets_split/readme.md
@@ -123,12 +123,12 @@ The EEPROM approach requires additional setup (flashing the eeeprom) but allows
 The USB cable approach is easier to setup and if you just want the usb cable on the left board, you do not need to do anything extra.
 
 ### Setting the left hand as master
-If you always plug the usb cable into the left board, nothing extra is needed as this is the default. Comment out `EE_HANDS` and comment out `I2C_MASTER_RIGHT` if for some reason it was set.
+If you always plug the usb cable into the left board, nothing extra is needed as this is the default. Comment out `EE_HANDS` and comment out `I2C_MASTER_RIGHT` or `MASTER_RIGHT` if for some reason it was set.
 
 ### Setting the right hand as master
 If you always plug the usb cable into the right board, add an extra flag to your `config.h`
 ```
- #define I2C_MASTER_RIGHT
+ #define MASTER_RIGHT
 ```
 
 ### Setting EE_hands to use either hands as master
diff --git a/keyboards/lets_split/split_util.c b/keyboards/lets_split/split_util.c
index 461921798f..226dc18816 100644
--- a/keyboards/lets_split/split_util.c
+++ b/keyboards/lets_split/split_util.c
@@ -21,7 +21,8 @@ static void setup_handedness(void) {
   #ifdef EE_HANDS
     isLeftHand = eeprom_read_byte(EECONFIG_HANDEDNESS);
   #else
-    #ifdef I2C_MASTER_RIGHT
+    // I2C_MASTER_RIGHT is deprecated use MASTER_RIGHT instead since this works for both serial and i2c
+    #if defined(I2C_MASTER_RIGHT) || defined(MASTER_RIGHT)
       isLeftHand = !has_usb();
     #else
       isLeftHand = has_usb();