diff --git a/libraries/AP_Mount/AP_Mount_Alexmos.h b/libraries/AP_Mount/AP_Mount_Alexmos.h
index a746e19459..88c19fb317 100644
--- a/libraries/AP_Mount/AP_Mount_Alexmos.h
+++ b/libraries/AP_Mount/AP_Mount_Alexmos.h
@@ -288,7 +288,7 @@ private:
         alexmos_angles angles;
         alexmos_params params;
         alexmos_angles_speed angle_speed;
-        uint8_t bytes[];
+        uint8_t bytes[1];
     } _buffer,_current_parameters;
 
     AP_HAL::UARTDriver *_port;
diff --git a/libraries/AP_Mount/AP_Mount_SToRM32_serial.h b/libraries/AP_Mount/AP_Mount_SToRM32_serial.h
index 1da8e49197..1bb9ede2ea 100644
--- a/libraries/AP_Mount/AP_Mount_SToRM32_serial.h
+++ b/libraries/AP_Mount/AP_Mount_SToRM32_serial.h
@@ -145,7 +145,7 @@ private:
     union PACKED SToRM32_reply {
         SToRM32_reply_data_struct data;
         SToRM32_reply_ack_struct ack;
-        uint8_t bytes[];
+        uint8_t bytes[1];
     } _buffer;
 
     // keep the last _current_angle values