diff --git a/src/hll/ChrLoader.c b/src/hll/ChrLoader.c
index 0258878..75de88e 100644
--- a/src/hll/ChrLoader.c
+++ b/src/hll/ChrLoader.c
@@ -95,10 +95,7 @@ static uint8_t *chr_get(int id)
 		free(data);
 		data = NULL;
 	} else {
-		struct mt19937 mt;
-		mt19937_init(&mt, 12753);
-		for (size_t i = 4; i < size; i++)
-			data[i] ^= mt19937_genrand(&mt);
+		mt19937_xorcode(data + 4, size - 4, 12753);
 		slot->value = data;
 	}
 	free(path);
diff --git a/src/hll/DataFile.c b/src/hll/DataFile.c
index 31b6f8e..eb6a355 100644
--- a/src/hll/DataFile.c
+++ b/src/hll/DataFile.c
@@ -274,10 +274,7 @@ static int DataFile_Open(int link)
 	uint8_t *compressed_data = xmalloc(compressed_size);
 	buffer_read_bytes(&r, compressed_data, compressed_size);
 	archive_free_data(dfile);
-	struct mt19937 mt;
-	mt19937_init(&mt, 4588163);
-	for (size_t i = 0; i < compressed_size; i++)
-		compressed_data[i] ^= mt19937_genrand(&mt);
+	mt19937_xorcode(compressed_data, compressed_size, 4588163);
 
 	uint8_t *raw = xmalloc(uncompressed_size);
 	int rv = uncompress(raw, &uncompressed_size, compressed_data, compressed_size);
diff --git a/src/hll/MapLoader.c b/src/hll/MapLoader.c
index cc988b5..7f66dca 100644
--- a/src/hll/MapLoader.c
+++ b/src/hll/MapLoader.c
@@ -95,10 +95,7 @@ static bool MapLoader_Load(int map_no)
 		free(map_data);
 		map_data = NULL;
 	} else {
-		struct mt19937 mt;
-		mt19937_init(&mt, 12753);
-		for (size_t i = 4; i < map_size; i++)
-			map_data[i] ^= mt19937_genrand(&mt);
+		mt19937_xorcode(map_data + 4, map_size - 4, 12753);
 	}
 	free(path);
 	return !!map_data;
diff --git a/subprojects/libsys4 b/subprojects/libsys4
index 7ee34d6..c5d3cb9 160000
--- a/subprojects/libsys4
+++ b/subprojects/libsys4
@@ -1 +1 @@
-Subproject commit 7ee34d622bb4c40f1d2524115e1eb6a2c58943c5
+Subproject commit c5d3cb955e2595456d5833918e55987f9c91fc88