diff --git a/src/newgrf.cpp b/src/newgrf.cpp
index f03fe35712..233085d1d5 100644
--- a/src/newgrf.cpp
+++ b/src/newgrf.cpp
@@ -451,6 +451,17 @@ GRFFile *GetFileByGRFID(uint32 grfid)
 	return nullptr;
 }
 
+/**
+ * Obtain a NewGRF file by its grfID,  expect it to usually be the current GRF's grfID
+ * @param grfid The grfID to obtain the file for
+ * @return The file.
+ */
+GRFFile *GetFileByGRFIDExpectCurrent(uint32 grfid)
+{
+	if (_cur.grffile->grfid == grfid) return _cur.grffile;
+	return GetFileByGRFID(grfid);
+}
+
 /**
  * Obtain a NewGRF file by its filename
  * @param filename The filename to obtain the file for.
@@ -11943,6 +11954,9 @@ void LoadNewGRF(uint load_index, uint num_baseset)
 
 	/* Pseudo sprite processing is finished; free temporary stuff */
 	_cur.ClearDataForNextFile();
+	for (GRFFile * const file : _grf_files) {
+		file->string_map.clear();
+	}
 
 	/* Call any functions that should be run after GRFs have been loaded. */
 	AfterLoadGRFs();
diff --git a/src/newgrf.h b/src/newgrf.h
index 1ee20a8dd5..200443a904 100644
--- a/src/newgrf.h
+++ b/src/newgrf.h
@@ -348,6 +348,8 @@ struct GRFFile : ZeroedMemoryAllocator {
 
 	byte ctrl_flags;                         ///< General GRF control flags
 
+	btree::btree_map<uint16, uint> string_map; ///< Map of local GRF string ID to string ID
+
 	GRFFile(const struct GRFConfig *config);
 	~GRFFile();
 
diff --git a/src/newgrf_text.cpp b/src/newgrf_text.cpp
index 9ca7e89f74..432e5b75e2 100644
--- a/src/newgrf_text.cpp
+++ b/src/newgrf_text.cpp
@@ -573,23 +573,30 @@ StringID AddGRFString(uint32 grfid, uint16 stringid, byte langid_to_add, bool ne
 	}
 
 	uint id;
-	for (id = 0; id < _num_grf_texts; id++) {
-		if (_grf_text[id].grfid == grfid && _grf_text[id].stringid == stringid) {
-			break;
-		}
-	}
+	extern GRFFile *GetFileByGRFIDExpectCurrent(uint32 grfid);
+	GRFFile *grf = GetFileByGRFIDExpectCurrent(grfid);
+	if (grf == nullptr) return STR_EMPTY;
 
-	/* Too many strings allocated, return empty */
-	if (id == lengthof(_grf_text)) {
-		_grf_bug_too_many_strings = true;
-		return STR_EMPTY;
+	auto iter = grf->string_map.lower_bound(stringid);
+	if (iter != grf->string_map.end() && iter->first == stringid) {
+		/* Found */
+		id = iter->second;
+	} else {
+		/* Allocate new ID */
+		id = _num_grf_texts;
+
+		/* Too many strings allocated, return empty */
+		if (id == lengthof(_grf_text)) {
+			_grf_bug_too_many_strings = true;
+			return STR_EMPTY;
+		}
+
+		grf->string_map.insert(iter, std::make_pair(stringid, id));
+		_num_grf_texts++;
 	}
 
 	std::string newtext = TranslateTTDPatchCodes(grfid, langid_to_add, allow_newlines, text_to_add);
 
-	/* If we didn't find our stringid and grfid in the list, allocate a new id */
-	if (id == _num_grf_texts) _num_grf_texts++;
-
 	if (_grf_text[id].textholder.empty()) {
 		_grf_text[id].grfid      = grfid;
 		_grf_text[id].stringid   = stringid;