diff --git a/pyproject.toml b/pyproject.toml
index 931c3ecf..5eca38c1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -19,7 +19,7 @@ license = { text = "Apache-2.0" }
 requires-python = ">=3.9"
 dependencies = [
     "nomad-lab>=1.2.0",
-    'matid>=2.0.0.dev2'
+    "matid>=2.0.0.dev2",
 ]
 
 [project.urls]
@@ -35,6 +35,7 @@ dev = [
     'pytest-cov==2.7.1',
     'ruff==0.1.8',
     "structlog==22.3.0",
+    "lxml>=4.6",
 ]
 
 [tool.ruff]