diff --git a/src/dynamics/thermal/heater.hpp b/src/dynamics/thermal/heater.hpp
index 6e3ce4673..e981b1fe3 100644
--- a/src/dynamics/thermal/heater.hpp
+++ b/src/dynamics/thermal/heater.hpp
@@ -46,7 +46,7 @@ class Heater {
    * @fn GetHeaterID
    * @brief Return Heater Id
    */
-  inline int GetHeaterId(void) const { return heater_id_; }
+  inline size_t GetHeaterId(void) const { return heater_id_; }
   /**
    * @fn GetPowerRating_W
    * @brief Return power rating [W]
diff --git a/src/environment/global/gnss_satellites.cpp b/src/environment/global/gnss_satellites.cpp
index 69d3ac63d..e12f979af 100644
--- a/src/environment/global/gnss_satellites.cpp
+++ b/src/environment/global/gnss_satellites.cpp
@@ -376,8 +376,8 @@ void GnssSat_position::SetUp(const double start_unix_time, const double step_sec
       continue;
     }
 
-    int64_t index = lower_bound(unixtime_vector_.at(gnss_satellite_id).begin(), unixtime_vector_.at(gnss_satellite_id).end(), start_unix_time) -
-                    unixtime_vector_.at(gnss_satellite_id).begin();
+    int index = lower_bound(unixtime_vector_.at(gnss_satellite_id).begin(), unixtime_vector_.at(gnss_satellite_id).end(), start_unix_time) -
+                unixtime_vector_.at(gnss_satellite_id).begin();
     if (index == (int)unixtime_vector_.at(gnss_satellite_id).size()) {
       nearest_index_.at(gnss_satellite_id) = index;
       validate_.at(gnss_satellite_id) = false;