diff --git a/headers/os/support/Archivable.h b/headers/os/support/Archivable.h
index 6f15977375..076a2a8ace 100644
--- a/headers/os/support/Archivable.h
+++ b/headers/os/support/Archivable.h
@@ -129,7 +129,7 @@ public:
 			void				AssumeOwnership(BArchivable* archivable);
 			void				RelinquishOwnership(BArchivable* archivable);
 
-	static	bool				IsArchiveManaged(BMessage* archive);
+	static	bool				IsArchiveManaged(const BMessage* archive);
 	static	BMessage*			PrepareArchive(BMessage*& archive);
 
 	template<class T>
diff --git a/src/kits/support/Archivable.cpp b/src/kits/support/Archivable.cpp
index 2b08106446..7f84a20123 100644
--- a/src/kits/support/Archivable.cpp
+++ b/src/kits/support/Archivable.cpp
@@ -452,6 +452,7 @@ BUnarchiver::FindObject<BArchivable>(const char* name,
 bool
 BUnarchiver::IsInstantiated(int32 token)
 {
+	_CallDebuggerIfManagerNull();
 	return fManager->IsInstantiated(token);
 }
 
@@ -504,7 +505,7 @@ BUnarchiver::RelinquishOwnership(BArchivable* archivable)
 
 
 bool
-BUnarchiver::IsArchiveManaged(BMessage* archive)
+BUnarchiver::IsArchiveManaged(const BMessage* archive)
 {
 	// managed child archives will return here
 	if (BManagerBase::ManagerPointer(archive))