diff -Naur firefox-52.9.0esr.orig/extensions/spellcheck/src/mozSpellChecker.h firefox-52.9.0esr/extensions/spellcheck/src/mozSpellChecker.h
--- firefox-52.9.0esr.orig/extensions/spellcheck/src/mozSpellChecker.h	2024-01-07 15:58:46.604431217 +0100
+++ firefox-52.9.0esr/extensions/spellcheck/src/mozSpellChecker.h	2024-01-07 16:00:47.739420245 +0100
@@ -17,7 +17,7 @@
 #include "nsTArray.h"
 #include "mozISpellI18NUtil.h"
 #include "nsCycleCollectionParticipant.h"
-#include "RemoteSpellCheckEngineChild.h"
+#include "mozilla/RemoteSpellCheckEngineChild.h"
 
 namespace mozilla {
 class PRemoteSpellcheckEngineChild;