diff --git a/libraries/AP_Compass/AP_Compass.cpp b/libraries/AP_Compass/AP_Compass.cpp
index 53930359ff..8cc61c8dde 100644
--- a/libraries/AP_Compass/AP_Compass.cpp
+++ b/libraries/AP_Compass/AP_Compass.cpp
@@ -1153,6 +1153,18 @@ void Compass::_probe_external_i2c_compasses(void)
     }
 #endif
 
+#if !defined(HAL_DISABLE_I2C_MAGS_BY_DEFAULT) || defined(HAL_USE_I2C_MAG_MMC3416)
+    // external i2c bus
+    FOREACH_I2C_EXTERNAL(i) {
+        ADD_BACKEND(DRIVER_MMC3416, AP_Compass_MMC3416::probe(GET_I2C_DEVICE(i, HAL_COMPASS_MMC3416_I2C_ADDR),
+                    true, ROTATION_NONE));
+    }
+    FOREACH_I2C_INTERNAL(i) {
+        ADD_BACKEND(DRIVER_MMC3416, AP_Compass_MMC3416::probe(GET_I2C_DEVICE(i, HAL_COMPASS_MMC3416_I2C_ADDR),
+                    all_external, ROTATION_NONE));
+    }
+#endif
+
 #if !defined(HAL_DISABLE_I2C_MAGS_BY_DEFAULT) || defined(HAL_USE_I2C_MAG_RM3100)
 #ifdef HAL_COMPASS_RM3100_I2C_ADDR
     const uint8_t rm3100_addresses[] = { HAL_COMPASS_RM3100_I2C_ADDR };