diff --git a/libraries/AP_Motors/AP_Motors6DOF.h b/libraries/AP_Motors/AP_Motors6DOF.h
index ff356e7f14..72a70409fc 100644
--- a/libraries/AP_Motors/AP_Motors6DOF.h
+++ b/libraries/AP_Motors/AP_Motors6DOF.h
@@ -29,7 +29,7 @@ public:
         SUB_FRAME_CUSTOM
     } sub_frame_t;
 
-    const char* get_frame_string() override { return _frame_class_string; };
+    const char* get_frame_string() const override { return _frame_class_string; };
 
     // Override parent
     void setup_motors(motor_frame_class frame_class, motor_frame_type frame_type) override;
diff --git a/libraries/AP_Motors/AP_MotorsCoax.h b/libraries/AP_Motors/AP_MotorsCoax.h
index ba7b9fc0a3..d02e3bcd98 100644
--- a/libraries/AP_Motors/AP_MotorsCoax.h
+++ b/libraries/AP_Motors/AP_MotorsCoax.h
@@ -49,7 +49,7 @@ public:
     //  this can be used to ensure other pwm outputs (i.e. for servos) do not conflict
     uint16_t            get_motor_mask() override;
 
-    const char* get_frame_string() override { return "COAX"; }
+    const char* get_frame_string() const override { return "COAX"; }
 
 protected:
     // output - sends commands to the motors
diff --git a/libraries/AP_Motors/AP_MotorsHeli.h b/libraries/AP_Motors/AP_MotorsHeli.h
index d73c69caee..9539d24969 100644
--- a/libraries/AP_Motors/AP_MotorsHeli.h
+++ b/libraries/AP_Motors/AP_MotorsHeli.h
@@ -159,7 +159,7 @@ public:
     // var_info for holding Parameter information
     static const struct AP_Param::GroupInfo var_info[];
 
-    const char* get_frame_string() override { return "HELI"; }
+    const char* get_frame_string() const override { return "HELI"; }
 
 protected:
 
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Dual.h b/libraries/AP_Motors/AP_MotorsHeli_Dual.h
index fa11e67e73..1ca8cb2a7f 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Dual.h
+++ b/libraries/AP_Motors/AP_MotorsHeli_Dual.h
@@ -99,7 +99,7 @@ public:
     // var_info for holding Parameter information
     static const struct AP_Param::GroupInfo var_info[];
 
-    const char* get_frame_string() override { return "HELI_DUAL"; }
+    const char* get_frame_string() const override { return "HELI_DUAL"; }
 
 protected:
 
diff --git a/libraries/AP_Motors/AP_MotorsHeli_Quad.h b/libraries/AP_Motors/AP_MotorsHeli_Quad.h
index 5ee66672cd..50909453d0 100644
--- a/libraries/AP_Motors/AP_MotorsHeli_Quad.h
+++ b/libraries/AP_Motors/AP_MotorsHeli_Quad.h
@@ -77,7 +77,7 @@ public:
     // var_info for holding Parameter information
     static const struct AP_Param::GroupInfo var_info[];
 
-    const char* get_frame_string() override { return "HELI_QUAD"; }
+    const char* get_frame_string() const override { return "HELI_QUAD"; }
 
 protected:
 
diff --git a/libraries/AP_Motors/AP_MotorsMatrix.cpp b/libraries/AP_Motors/AP_MotorsMatrix.cpp
index d9b729808b..122c8c8e88 100644
--- a/libraries/AP_Motors/AP_MotorsMatrix.cpp
+++ b/libraries/AP_Motors/AP_MotorsMatrix.cpp
@@ -42,7 +42,7 @@ void AP_MotorsMatrix::init(motor_frame_class frame_class, motor_frame_type frame
 // dedicated init for lua scripting
 bool AP_MotorsMatrix::init(uint8_t expected_num_motors)
 {
-    if (_last_frame_class != MOTOR_FRAME_SCRIPTING_MATRIX) {
+    if (_active_frame_class != MOTOR_FRAME_SCRIPTING_MATRIX) {
         // not the correct class
         return false;
     }
diff --git a/libraries/AP_Motors/AP_MotorsMatrix.h b/libraries/AP_Motors/AP_MotorsMatrix.h
index f1a8d9da00..ad69b7b38f 100644
--- a/libraries/AP_Motors/AP_MotorsMatrix.h
+++ b/libraries/AP_Motors/AP_MotorsMatrix.h
@@ -70,8 +70,9 @@ public:
     // using copter motors for forward flight
     float               get_roll_factor(uint8_t i) override { return _roll_factor[i]; }
 
-    const char*         get_frame_string() override { return _frame_class_string; }
-    const char*         get_type_string() override { return _frame_type_string; }
+    const char*         get_frame_string() const override { return _frame_class_string; }
+    const char*         get_type_string() const override { return _frame_type_string; }
+
     // disable the use of motor torque to control yaw. Used when an external mechanism such
     // as vectoring is used for yaw control
     void                disable_yaw_torque(void) override;
diff --git a/libraries/AP_Motors/AP_MotorsSingle.h b/libraries/AP_Motors/AP_MotorsSingle.h
index 5bdbe1006a..32317e9a10 100644
--- a/libraries/AP_Motors/AP_MotorsSingle.h
+++ b/libraries/AP_Motors/AP_MotorsSingle.h
@@ -49,7 +49,7 @@ public:
     //  this can be used to ensure other pwm outputs (i.e. for servos) do not conflict
     uint16_t            get_motor_mask() override;
 
-    const char* get_frame_string() override { return "SINGLE"; }
+    const char* get_frame_string() const override { return "SINGLE"; }
 
 protected:
     // output - sends commands to the motors
diff --git a/libraries/AP_Motors/AP_MotorsTailsitter.h b/libraries/AP_Motors/AP_MotorsTailsitter.h
index a2a26c508b..bf9f8a322d 100644
--- a/libraries/AP_Motors/AP_MotorsTailsitter.h
+++ b/libraries/AP_Motors/AP_MotorsTailsitter.h
@@ -33,7 +33,7 @@ public:
     //  this can be used to ensure other pwm outputs (i.e. for servos) do not conflict
     uint16_t get_motor_mask() override;
 
-    const char* get_frame_string() override { return "TAILSITTER"; }
+    const char* get_frame_string() const override { return "TAILSITTER"; }
 
 protected:
     // calculate motor outputs
diff --git a/libraries/AP_Motors/AP_MotorsTri.h b/libraries/AP_Motors/AP_MotorsTri.h
index 36bbb81d08..df3a0b895e 100644
--- a/libraries/AP_Motors/AP_MotorsTri.h
+++ b/libraries/AP_Motors/AP_MotorsTri.h
@@ -54,7 +54,7 @@ public:
     // using copter motors for forward flight
     float               get_roll_factor(uint8_t i) override;
 
-    const char* get_frame_string() override { return "TRI"; }
+    const char* get_frame_string() const override { return "TRI"; }
 
 protected:
     // output - sends commands to the motors
diff --git a/libraries/AP_Motors/AP_Motors_Class.h b/libraries/AP_Motors/AP_Motors_Class.h
index b172192c70..990feaada9 100644
--- a/libraries/AP_Motors/AP_Motors_Class.h
+++ b/libraries/AP_Motors/AP_Motors_Class.h
@@ -49,7 +49,7 @@ public:
     };
 
     // return string corresponding to frame_class
-    virtual const char* get_frame_string() = 0;
+    virtual const char* get_frame_string() const = 0;
 
     enum motor_frame_type {
         MOTOR_FRAME_TYPE_PLUS = 0,
@@ -71,7 +71,7 @@ public:
     };
 
     // return string corresponding to frame_type
-    virtual const char* get_type_string() { return ""; }
+    virtual const char* get_type_string() const { return ""; }
 
     // Constructor
     AP_Motors(uint16_t loop_rate, uint16_t speed_hz = AP_MOTORS_SPEED_DEFAULT);