diff --git a/mission/acs/str/StarTrackerHandler.h b/mission/acs/str/StarTrackerHandler.h
index 69b3e121..f143a660 100644
--- a/mission/acs/str/StarTrackerHandler.h
+++ b/mission/acs/str/StarTrackerHandler.h
@@ -54,9 +54,6 @@ class StarTrackerHandler : public DeviceHandlerBase {
 
   Submode_t getInitialSubmode() override;
 
-  static const Submode_t SUBMODE_BOOTLOADER = 1;
-  static const Submode_t SUBMODE_FIRMWARE = 2;
-
  protected:
   void doStartUp() override;
   void doShutDown() override;
diff --git a/mission/acs/str/strHelpers.h b/mission/acs/str/strHelpers.h
index 002d9934..4eea2635 100644
--- a/mission/acs/str/strHelpers.h
+++ b/mission/acs/str/strHelpers.h
@@ -11,6 +11,9 @@
 
 namespace startracker {
 
+static const Submode_t SUBMODE_BOOTLOADER = 1;
+static const Submode_t SUBMODE_FIRMWARE = 2;
+
 /**
  * @brief    Returns the frame type field of a decoded frame.
  */
diff --git a/mission/system/acs/StrAssembly.cpp b/mission/system/acs/StrAssembly.cpp
index abd7a4ce..574ad634 100644
--- a/mission/system/acs/StrAssembly.cpp
+++ b/mission/system/acs/StrAssembly.cpp
@@ -2,6 +2,8 @@
 
 #include <eive/objects.h>
 
+#include "mission/acs/str/strHelpers.h"
+
 StrAssembly::StrAssembly(object_id_t objectId) : AssemblyBase(objectId) {
   ModeListEntry entry;
   entry.setObject(objects::STAR_TRACKER);
@@ -31,5 +33,12 @@ ReturnValue_t StrAssembly::checkChildrenStateOn(Mode_t wantedMode, Submode_t wan
 }
 
 ReturnValue_t StrAssembly::isModeCombinationValid(Mode_t mode, Submode_t submode) {
+  if (mode == DeviceHandlerIF::MODE_NORMAL and submode != SUBMODE_NONE) {
+    return HasModesIF::INVALID_SUBMODE;
+  }
+  if (mode == MODE_ON and
+      (submode != startracker::SUBMODE_BOOTLOADER and submode != startracker::SUBMODE_FIRMWARE)) {
+    return HasModesIF::INVALID_SUBMODE;
+  }
   return returnvalue::OK;
 }
diff --git a/tmtc b/tmtc
index 50668ca7..dcf7d0af 160000
--- a/tmtc
+++ b/tmtc
@@ -1 +1 @@
-Subproject commit 50668ca7a74edd4219456e393cd10f7858591130
+Subproject commit dcf7d0af71f6ba9d569f9f56604e9245a0233427