diff --git a/keyboards/dark_project/cm81/config.h b/keyboards/dark_project/cm81/config.h
index e2e3f496c04..db4036f48cd 100644
--- a/keyboards/dark_project/cm81/config.h
+++ b/keyboards/dark_project/cm81/config.h
@@ -20,6 +20,7 @@
 #define I2C1_SDA_PIN B7
 #define I2C1_SCL_PIN B6
 #define I2C1_CLOCK_SPEED 400000 /* 400000 */
+#define I2C1_OPMODE OPMODE_I2C
 
 #define LED_MAC_OS_PIN B13
 #define LED_WIN_LOCK_PIN B14