diff --git a/libraries/AP_Compass/AP_Compass_AK09916.cpp b/libraries/AP_Compass/AP_Compass_AK09916.cpp
index bb6732365a..8630da5e97 100644
--- a/libraries/AP_Compass/AP_Compass_AK09916.cpp
+++ b/libraries/AP_Compass/AP_Compass_AK09916.cpp
@@ -58,13 +58,6 @@ extern const AP_HAL::HAL &hal;
 
 extern const AP_HAL::HAL &hal;
 
-struct PACKED sample_regs {
-    uint8_t st1;
-    int16_t val[3];
-    uint8_t tmps;
-    uint8_t st2;
-};
-
 AP_Compass_AK09916::AP_Compass_AK09916(AP_AK09916_BusDriver *bus,
                                         bool force_external,
                                         enum Rotation rotation)
@@ -477,7 +470,7 @@ bool AP_AK09916_BusDriver_Auxiliary::configure()
 
 bool AP_AK09916_BusDriver_Auxiliary::start_measurements()
 {
-    if (_bus->register_periodic_read(_slave, REG_ST1, sizeof(sample_regs)) < 0) {
+    if (_bus->register_periodic_read(_slave, REG_ST1, sizeof(AP_Compass_AK09916::sample_regs)) < 0) {
         return false;
     }
 
diff --git a/libraries/AP_Compass/AP_Compass_AK09916.h b/libraries/AP_Compass/AP_Compass_AK09916.h
index b4cca6e973..5c80cff9ef 100644
--- a/libraries/AP_Compass/AP_Compass_AK09916.h
+++ b/libraries/AP_Compass/AP_Compass_AK09916.h
@@ -75,6 +75,14 @@ public:
 
     void read() override;
 
+    /* Must be public so the BusDriver can access its definition */
+    struct PACKED sample_regs {
+        uint8_t st1;
+        int16_t val[3];
+        uint8_t tmps;
+        uint8_t st2;
+    };
+
 private:
     AP_Compass_AK09916(AP_AK09916_BusDriver *bus, bool force_external,
                        enum Rotation rotation);
diff --git a/libraries/AP_Compass/AP_Compass_AK8963.cpp b/libraries/AP_Compass/AP_Compass_AK8963.cpp
index 4c4ced9e3f..ad6a8c6d23 100644
--- a/libraries/AP_Compass/AP_Compass_AK8963.cpp
+++ b/libraries/AP_Compass/AP_Compass_AK8963.cpp
@@ -49,11 +49,6 @@
 
 #define AK8963_MILLIGAUSS_SCALE 10.0f
 
-struct PACKED sample_regs {
-    int16_t val[3];
-    uint8_t st2;
-};
-
 extern const AP_HAL::HAL &hal;
 
 AP_Compass_AK8963::AP_Compass_AK8963(AP_AK8963_BusDriver *bus,
@@ -379,7 +374,7 @@ bool AP_AK8963_BusDriver_Auxiliary::configure()
 
 bool AP_AK8963_BusDriver_Auxiliary::start_measurements()
 {
-    if (_bus->register_periodic_read(_slave, AK8963_HXL, sizeof(sample_regs)) < 0) {
+    if (_bus->register_periodic_read(_slave, AK8963_HXL, sizeof(AP_Compass_AK8963::sample_regs)) < 0) {
         return false;
     }
 
diff --git a/libraries/AP_Compass/AP_Compass_AK8963.h b/libraries/AP_Compass/AP_Compass_AK8963.h
index 7b61768d84..c0f0207565 100644
--- a/libraries/AP_Compass/AP_Compass_AK8963.h
+++ b/libraries/AP_Compass/AP_Compass_AK8963.h
@@ -39,6 +39,12 @@ public:
 
     void read() override;
 
+    /* Must be public so the BusDriver can access its definition */
+    struct PACKED sample_regs {
+        int16_t val[3];
+        uint8_t st2;
+    };
+
 private:
     AP_Compass_AK8963(AP_AK8963_BusDriver *bus,
                       enum Rotation rotation);
diff --git a/libraries/AP_Compass/AP_Compass_LSM9DS1.cpp b/libraries/AP_Compass/AP_Compass_LSM9DS1.cpp
index eeebe00fdc..60db0f54de 100644
--- a/libraries/AP_Compass/AP_Compass_LSM9DS1.cpp
+++ b/libraries/AP_Compass/AP_Compass_LSM9DS1.cpp
@@ -47,11 +47,6 @@
 #define LSM9DS1M_INT_THS_L_M        0x32
 #define LSM9DS1M_INT_THS_H_M        0x33
 
-struct PACKED sample_regs {
-    uint8_t status;
-    int16_t val[3];
-};
-
 extern const AP_HAL::HAL &hal;
 
 AP_Compass_LSM9DS1::AP_Compass_LSM9DS1(AP_HAL::OwnPtr<AP_HAL::Device> dev,
diff --git a/libraries/AP_Compass/AP_Compass_LSM9DS1.h b/libraries/AP_Compass/AP_Compass_LSM9DS1.h
index 2cb91c74c6..7017883bd6 100644
--- a/libraries/AP_Compass/AP_Compass_LSM9DS1.h
+++ b/libraries/AP_Compass/AP_Compass_LSM9DS1.h
@@ -42,6 +42,11 @@ private:
     uint8_t _compass_instance;
     float _scaling;
     enum Rotation _rotation;
+
+    struct PACKED sample_regs {
+        uint8_t status;
+        int16_t val[3];
+    };
 };
 
 #endif