diff --git a/radio/src/targets/taranis/hal.h b/radio/src/targets/taranis/hal.h
index 126d78f41..54a102c4c 100644
--- a/radio/src/targets/taranis/hal.h
+++ b/radio/src/targets/taranis/hal.h
@@ -326,6 +326,8 @@
 #define I2C_GPIO_PinSource_SDA          GPIO_PinSource7
 #if defined(REVPLUS)
   #define I2C_SPEED                     400000
+#elif defined(REV4a)
+  #define I2C_SPEED                     100000
 #else
   #define I2C_SPEED                     200000
 #endif