diff --git a/src/hunter_sdk/hunter_base/include/hunter_base/hunter_types.hpp b/src/hunter_sdk/hunter_base/include/hunter_base/hunter_types.hpp
index 7ab420b..203041b 100644
--- a/src/hunter_sdk/hunter_base/include/hunter_base/hunter_types.hpp
+++ b/src/hunter_sdk/hunter_base/include/hunter_base/hunter_types.hpp
@@ -33,7 +33,8 @@ struct HunterState
     uint8_t set_zero_steering = 0;
 
     // motor state
-    MotorState motor_states[3];
+    static constexpr uint8_t motor_num = 3;
+    MotorState motor_states[motor_num];
 
     // motion state
     double linear_velocity = 0;
diff --git a/src/hunter_sdk/hunter_base/src/hunter_base.cpp b/src/hunter_sdk/hunter_base/src/hunter_base.cpp
index 0818978..5849ad8 100644
--- a/src/hunter_sdk/hunter_base/src/hunter_base.cpp
+++ b/src/hunter_sdk/hunter_base/src/hunter_base.cpp
@@ -229,7 +229,7 @@ void HunterBase::UpdateHunterState(const HunterMessage &status_msg,
       // std::cout << "motor 1 driver feedback received" << std::endl;
       const MotorDriverStatusMessage &msg =
           status_msg.body.motor_driver_status_msg;
-      for (int i = 0; i < 4; ++i) {
+      for (int i = 0; i < HunterState::motor_num; ++i) {
         state.motor_states[status_msg.body.motor_driver_status_msg.motor_id]
             .current =
             (static_cast<uint16_t>(msg.data.status.current.low_byte) |
diff --git a/src/scout_sdk/scout_base/include/scout_base/scout_types.hpp b/src/scout_sdk/scout_base/include/scout_base/scout_types.hpp
index 6767a0e..120531f 100644
--- a/src/scout_sdk/scout_base/include/scout_base/scout_types.hpp
+++ b/src/scout_sdk/scout_base/include/scout_base/scout_types.hpp
@@ -45,7 +45,8 @@ struct ScoutState
     double battery_voltage = 0.0;
 
     // motor state
-    MotorState motor_states[4];
+    static constexpr uint8_t motor_num = 4;
+    MotorState motor_states[motor_num];
 
     // light state
     bool light_control_enabled = false;
diff --git a/src/scout_sdk/scout_base/src/scout_base.cpp b/src/scout_sdk/scout_base/src/scout_base.cpp
index 0d7cc60..35a0afb 100644
--- a/src/scout_sdk/scout_base/src/scout_base.cpp
+++ b/src/scout_sdk/scout_base/src/scout_base.cpp
@@ -325,7 +325,7 @@ void ScoutBase::UpdateScoutState(const ScoutMessage &status_msg, ScoutState &sta
     {
         // std::cout << "motor 1 driver feedback received" << std::endl;
         const MotorDriverStatusMessage &msg = status_msg.body.motor_driver_status_msg;
-        for (int i = 0; i < 4; ++i)
+        for (int i = 0; i < ScoutState::motor_num; ++i)
         {
             state.motor_states[status_msg.body.motor_driver_status_msg.motor_id].current = (static_cast<uint16_t>(msg.data.status.current.low_byte) | static_cast<uint16_t>(msg.data.status.current.high_byte) << 8) / 10.0;
             state.motor_states[status_msg.body.motor_driver_status_msg.motor_id].rpm = static_cast<int16_t>(static_cast<uint16_t>(msg.data.status.rpm.low_byte) | static_cast<uint16_t>(msg.data.status.rpm.high_byte) << 8);