diff --git a/tools/kabukicho/gen_signs.py b/tools/kabukicho/gen_signs.py
index b6f03cd..a14314a 100644
--- a/tools/kabukicho/gen_signs.py
+++ b/tools/kabukicho/gen_signs.py
@@ -15,7 +15,7 @@
 OUT = sys.argv[1] if len(sys.argv) > 1 else os.path.join(os.path.dirname(__file__), "..", "generated", "textures")
 os.makedirs(OUT, exist_ok=True)
 
-FONT_DIR = "/System/Library/Fonts"
+FONT_DIR = os.environ.get("THREERT_FONT_DIR", "/System/Library/Fonts")
 GOTHIC = {w: os.path.join(FONT_DIR, f"ヒラギノ角ゴシック W{w}.ttc") for w in range(0, 10)}
 MINCHO = os.path.join(FONT_DIR, "ヒラギノ明朝 ProN.ttc")
 MARU = os.path.join(FONT_DIR, "ヒラギノ丸ゴ ProN W4.ttc")