diff --git a/src/CPUSensorMain.cpp b/src/CPUSensorMain.cpp
index eb619b9..de8607b 100644
--- a/src/CPUSensorMain.cpp
+++ b/src/CPUSensorMain.cpp
@@ -775,4 +775,5 @@
 
     setupManufacturingModeMatch(*systemBus);
     io.run();
+    return 0;
 }
diff --git a/src/ExitAirTempSensor.cpp b/src/ExitAirTempSensor.cpp
index 1cd55b8..c0aae42 100644
--- a/src/ExitAirTempSensor.cpp
+++ b/src/ExitAirTempSensor.cpp
@@ -1002,4 +1002,5 @@
     }
 
     io.run();
+    return 0;
 }
diff --git a/src/FanMain.cpp b/src/FanMain.cpp
index 30f0ca4..465ce1b 100644
--- a/src/FanMain.cpp
+++ b/src/FanMain.cpp
@@ -527,4 +527,5 @@
 
     setupManufacturingModeMatch(*systemBus);
     io.run();
+    return 0;
 }
diff --git a/src/MCUTempSensor.cpp b/src/MCUTempSensor.cpp
index 2f5e64c..cdc4fea 100644
--- a/src/MCUTempSensor.cpp
+++ b/src/MCUTempSensor.cpp
@@ -312,4 +312,5 @@
 
     setupManufacturingModeMatch(*systemBus);
     io.run();
+    return 0;
 }