diff --git a/precheck/precheck.py b/precheck/precheck.py
index 54ae9a8..41a95eb 100644
--- a/precheck/precheck.py
+++ b/precheck/precheck.py
@@ -9,7 +9,6 @@ import time
 import traceback
 import xml.etree.ElementTree as ET
 
-import brotli
 import gdstk
 import klayout.db as pya
 import klayout.rdb as rdb
@@ -282,17 +281,16 @@ def main():
         gds_stem = args.gds.removesuffix(".gds")
         gds_temp = None
         gds_file = args.gds
-    elif args.gds.endswith(".gds.br"):
-        gds_stem = args.gds.removesuffix(".gds.br")
+    elif args.gds.endswith(".oas"):
+        gds_stem = args.gds.removesuffix(".oas")
         gds_temp = tempfile.NamedTemporaryFile(suffix=".gds", delete=False)
         gds_file = gds_temp.name
-        logging.info(f"decompressing {args.gds} to {gds_file}")
-        with open(args.gds, "rb") as f:
-            data = f.read()
-        with open(gds_file, "wb") as f:
-            f.write(brotli.decompress(data))
+        logging.info(f"Converting {args.gds} to {gds_file}")
+        layout = pya.Layout()
+        layout.read(args.gds)
+        layout.write(gds_file)
     else:
-        raise PrecheckFailure("Layout file extension is neither .gds nor .gds.br")
+        raise PrecheckFailure("Layout file extension is neither .gds nor .oas")
 
     tech = args.tech
     if tech not in tech_names:
diff --git a/precheck/pyproject.toml b/precheck/pyproject.toml
index b09ddc3..9b68a34 100644
--- a/precheck/pyproject.toml
+++ b/precheck/pyproject.toml
@@ -3,7 +3,6 @@ name = "tt-precheck"
 requires-python = ">=3.11"
 dynamic = ["version"]
 dependencies = [
-    "brotli",
     "gdstk",
     "klayout>=0.28.17.post1,<0.29.0",
     "numpy<2",
diff --git a/precheck/requirements.txt b/precheck/requirements.txt
index e2cc11c..83c6340 100644
--- a/precheck/requirements.txt
+++ b/precheck/requirements.txt
@@ -1,11 +1,9 @@
 #
-# This file is autogenerated by pip-compile with Python 3.13
+# This file is autogenerated by pip-compile with Python 3.12
 # by the following command:
 #
 #    pip-compile
 #
-brotli==1.1.0
-    # via tt-precheck (pyproject.toml)
 gdstk==0.9.52
     # via tt-precheck (pyproject.toml)
 iniconfig==2.0.0