diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp b/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp
index 93a4c10b54..b9aa1914b8 100644
--- a/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow.cpp
@@ -160,7 +160,7 @@ void AP_OpticalFlow::init(uint32_t log_bit)
 #endif
         break;
     case Type::SITL:
-#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
+#if AP_OPTICALFLOW_SITL_ENABLED
         backend = new AP_OpticalFlow_SITL(*this);
 #endif
         break;
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow.h b/libraries/AP_OpticalFlow/AP_OpticalFlow.h
index 6b91b2ad0b..67de7287c8 100644
--- a/libraries/AP_OpticalFlow/AP_OpticalFlow.h
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow.h
@@ -24,6 +24,10 @@
 #define HAL_MSP_OPTICALFLOW_ENABLED (AP_OPTICALFLOW_ENABLED && (HAL_MSP_ENABLED && !HAL_MINIMIZE_FEATURES))
 #endif
 
+#ifndef AP_OPTICALFLOW_SITL_ENABLED
+#define AP_OPTICALFLOW_SITL_ENABLED AP_SIM_ENABLED
+#endif
+
 #if AP_OPTICALFLOW_ENABLED
 
 /*
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_Backend.h b/libraries/AP_OpticalFlow/AP_OpticalFlow_Backend.h
index 565d02ea05..059e5b92d1 100644
--- a/libraries/AP_OpticalFlow/AP_OpticalFlow_Backend.h
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_Backend.h
@@ -32,7 +32,7 @@ public:
     CLASS_NO_COPY(OpticalFlow_backend);
 
     // init - initialise sensor
-    virtual void init() = 0;
+    virtual void init() {}
 
     // read latest values from sensor and fill in x,y and totals.
     virtual void update() = 0;
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_SITL.cpp b/libraries/AP_OpticalFlow/AP_OpticalFlow_SITL.cpp
index e2b387b64d..5ac842daba 100644
--- a/libraries/AP_OpticalFlow/AP_OpticalFlow_SITL.cpp
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_SITL.cpp
@@ -17,26 +17,17 @@
  * AP_OpticalFlow_SITL.cpp - SITL emulation of optical flow sensor.
  */
 
-#include <AP_HAL/AP_HAL.h>
-
-#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
-
 #include "AP_OpticalFlow_SITL.h"
 
-extern const AP_HAL::HAL& hal;
+#if AP_OPTICALFLOW_SITL_ENABLED
 
-AP_OpticalFlow_SITL::AP_OpticalFlow_SITL(AP_OpticalFlow &_frontend) :
-    OpticalFlow_backend(_frontend),
-    _sitl(AP::sitl())
-{
-}
-
-void AP_OpticalFlow_SITL::init(void)
-{
-}
+#include <AP_HAL/AP_HAL.h>
+#include <SITL/SITL.h>
 
 void AP_OpticalFlow_SITL::update(void)
 {
+    auto *_sitl = AP::sitl();
+
     if (!_sitl->flow_enable) {
         return;
     }
@@ -128,4 +119,4 @@ void AP_OpticalFlow_SITL::update(void)
     _update_frontend(state);
 }
 
-#endif // CONFIG_HAL_BOARD
+#endif  // AP_OPTICALFLOW_SITL_ENABLED
diff --git a/libraries/AP_OpticalFlow/AP_OpticalFlow_SITL.h b/libraries/AP_OpticalFlow/AP_OpticalFlow_SITL.h
index bcf2157c83..e54cdc8e9c 100644
--- a/libraries/AP_OpticalFlow/AP_OpticalFlow_SITL.h
+++ b/libraries/AP_OpticalFlow/AP_OpticalFlow_SITL.h
@@ -1,27 +1,25 @@
 #pragma once
 
 #include "AP_OpticalFlow.h"
-#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
-#include <SITL/SITL.h>
+
+#if AP_OPTICALFLOW_SITL_ENABLED
 
 class AP_OpticalFlow_SITL : public OpticalFlow_backend
 {
 public:
     /// constructor
-    AP_OpticalFlow_SITL(AP_OpticalFlow &_frontend);
-
-    // init - initialise the sensor
-    void init() override;
+    using OpticalFlow_backend::OpticalFlow_backend;
 
     // update - read latest values from sensor and fill in x,y and totals.
     void update(void) override;
 
 private:
-    SITL::SIM *_sitl;
+
     uint32_t last_flow_ms;
 
     uint8_t next_optflow_index;
     uint8_t optflow_delay;
     AP_OpticalFlow::OpticalFlow_state optflow_data[20];
 };
-#endif // CONFIG_HAL_BOARD
+
+#endif  // AP_OPTICALFLOW_SITL_ENABLED