diff --git a/libraries/AP_IRLock/AP_IRLock_I2C.cpp b/libraries/AP_IRLock/AP_IRLock_I2C.cpp
index ce2dfef5d1..d0af466ac1 100644
--- a/libraries/AP_IRLock/AP_IRLock_I2C.cpp
+++ b/libraries/AP_IRLock/AP_IRLock_I2C.cpp
@@ -32,9 +32,13 @@ extern const AP_HAL::HAL& hal;
 
 #define IRLOCK_SYNC			0xAA55AA55
 
-void AP_IRLock_I2C::init()
+void AP_IRLock_I2C::init(int8_t bus)
 {
-    dev = std::move(hal.i2c_mgr->get_device(1, IRLOCK_I2C_ADDRESS));
+    if (bus < 0) {
+        // default to i2c external bus
+        bus = 1;
+    }
+    dev = std::move(hal.i2c_mgr->get_device(bus, IRLOCK_I2C_ADDRESS));
     if (!dev) {
         return;
     }
diff --git a/libraries/AP_IRLock/AP_IRLock_I2C.h b/libraries/AP_IRLock/AP_IRLock_I2C.h
index 80238a41df..1262eaefc1 100644
--- a/libraries/AP_IRLock/AP_IRLock_I2C.h
+++ b/libraries/AP_IRLock/AP_IRLock_I2C.h
@@ -10,7 +10,7 @@ class AP_IRLock_I2C : public IRLock
 {
 public:
     // init - initialize sensor library
-    void init();
+    void init(int8_t bus) override;
 
     // retrieve latest sensor data - returns true if new data is available
     bool update();
diff --git a/libraries/AP_IRLock/AP_IRLock_SITL.cpp b/libraries/AP_IRLock/AP_IRLock_SITL.cpp
index 32d44c02df..5601347e2a 100644
--- a/libraries/AP_IRLock/AP_IRLock_SITL.cpp
+++ b/libraries/AP_IRLock/AP_IRLock_SITL.cpp
@@ -36,7 +36,7 @@ AP_IRLock_SITL::AP_IRLock_SITL() :
     sock(true)
 {}
 
-void AP_IRLock_SITL::init()
+void AP_IRLock_SITL::init(int8_t bus)
 {
     SITL::SITL *sitl = (SITL::SITL *)AP_Param::find_object("SIM_");
     // try to bind to a specific port so that if we restart ArduPilot
diff --git a/libraries/AP_IRLock/AP_IRLock_SITL.h b/libraries/AP_IRLock/AP_IRLock_SITL.h
index e43a79470a..9f59c99a79 100644
--- a/libraries/AP_IRLock/AP_IRLock_SITL.h
+++ b/libraries/AP_IRLock/AP_IRLock_SITL.h
@@ -16,7 +16,7 @@ public:
     AP_IRLock_SITL();
 
     // init - initialize sensor library
-    virtual void init();
+    virtual void init(int8_t bus);
 
     // retrieve latest sensor data - returns true if new data is available
     virtual bool update();
diff --git a/libraries/AP_IRLock/IRLock.h b/libraries/AP_IRLock/IRLock.h
index f8e802a8e1..6d888b2568 100644
--- a/libraries/AP_IRLock/IRLock.h
+++ b/libraries/AP_IRLock/IRLock.h
@@ -28,7 +28,7 @@ class IRLock
 public:
     // init - initialize sensor library
     // library won't be useable unless this is first called
-    virtual void init() = 0;
+    virtual void init(int8_t bus) = 0;
 
     // true if irlock sensor is online and healthy
     bool healthy() const { return _flags.healthy; }