diff --git a/src/fsfw/devicehandlers/AssemblyBase.cpp b/src/fsfw/devicehandlers/AssemblyBase.cpp
index c29022e5..45f62ba0 100644
--- a/src/fsfw/devicehandlers/AssemblyBase.cpp
+++ b/src/fsfw/devicehandlers/AssemblyBase.cpp
@@ -196,7 +196,7 @@ ReturnValue_t AssemblyBase::checkModeCommand(Mode_t mode, Submode_t submode,
   }
 
   if ((mode != MODE_ON) && (mode != DeviceHandlerIF::MODE_NORMAL)) {
-    return INVALID_MODE;
+    return INVALID_MODE_RETVAL;
   }
 
   if (internalState != STATE_NONE) {
diff --git a/src/fsfw/devicehandlers/DeviceHandlerBase.cpp b/src/fsfw/devicehandlers/DeviceHandlerBase.cpp
index 1e87e8a7..65c5a946 100644
--- a/src/fsfw/devicehandlers/DeviceHandlerBase.cpp
+++ b/src/fsfw/devicehandlers/DeviceHandlerBase.cpp
@@ -403,7 +403,7 @@ ReturnValue_t DeviceHandlerBase::isModeCombinationValid(Mode_t mode, Submode_t s
         return INVALID_SUBMODE;
       }
     default:
-      return HasModesIF::INVALID_MODE;
+      return HasModesIF::INVALID_MODE_RETVAL;
   }
 }
 
diff --git a/src/fsfw/modes/HasModesIF.h b/src/fsfw/modes/HasModesIF.h
index 850d4349..d59e0294 100644
--- a/src/fsfw/modes/HasModesIF.h
+++ b/src/fsfw/modes/HasModesIF.h
@@ -13,7 +13,7 @@ class HasModesIF {
 
  public:
   static const uint8_t INTERFACE_ID = CLASS_ID::HAS_MODES_IF;
-  static const ReturnValue_t INVALID_MODE = MAKE_RETURN_CODE(0x01);
+  static const ReturnValue_t INVALID_MODE_RETVAL = MAKE_RETURN_CODE(0x01);
   static const ReturnValue_t TRANS_NOT_ALLOWED = MAKE_RETURN_CODE(0x02);
   static const ReturnValue_t IN_TRANSITION = MAKE_RETURN_CODE(0x03);
   static const ReturnValue_t INVALID_SUBMODE = MAKE_RETURN_CODE(0x04);
@@ -37,9 +37,13 @@ class HasModesIF {
   //! The device is powered and ready to perform operations. In this mode, no commands are
   //! sent by the device handler itself, but direct commands van be commanded and will be
   //! interpreted
-  static const Mode_t MODE_ON = 1;
+  static constexpr Mode_t MODE_ON = 1;
   //! The device is powered off. The only command accepted in this mode is a mode change to on.
-  static const Mode_t MODE_OFF = 0;
+  static constexpr Mode_t MODE_OFF = 0;
+
+  static constexpr Mode_t INVALID_MODE = -1;
+  static constexpr Mode_t UNDEFINED_MODE = -2;
+
   //! To avoid checks against magic number "0".
   static const Submode_t SUBMODE_NONE = 0;
 
diff --git a/src/fsfw/subsystem/SubsystemBase.cpp b/src/fsfw/subsystem/SubsystemBase.cpp
index f177ecd4..71c47c5f 100644
--- a/src/fsfw/subsystem/SubsystemBase.cpp
+++ b/src/fsfw/subsystem/SubsystemBase.cpp
@@ -33,8 +33,9 @@ ReturnValue_t SubsystemBase::registerChild(object_id_t objectId) {
       info.mode = MODE_OFF;
     }
   } else {
+    // intentional to force an initial command during system startup
     info.commandQueue = child->getCommandQueue();
-    info.mode = -1;  // intentional to force an initial command during system startup
+    info.mode = HasModesIF::UNDEFINED_MODE;
   }
 
   info.submode = SUBMODE_NONE;
diff --git a/tests/src/fsfw_tests/integration/assemblies/TestAssembly.cpp b/tests/src/fsfw_tests/integration/assemblies/TestAssembly.cpp
index a0313f96..8e79bbc6 100644
--- a/tests/src/fsfw_tests/integration/assemblies/TestAssembly.cpp
+++ b/tests/src/fsfw_tests/integration/assemblies/TestAssembly.cpp
@@ -125,7 +125,7 @@ ReturnValue_t TestAssembly::isModeCombinationValid(Mode_t mode, Submode_t submod
         return INVALID_SUBMODE;
       }
   }
-  return INVALID_MODE;
+  return INVALID_MODE_RETVAL;
 }
 
 ReturnValue_t TestAssembly::initialize() {