diff --git a/services/data/requirements.txt b/services/data/requirements.txt
index 3cde598..831bafd 100644
--- a/services/data/requirements.txt
+++ b/services/data/requirements.txt
@@ -1,6 +1,6 @@
 # Data service — IfcOpenShell extraction, QA & clash (guide §8 + analysis)
 ifcopenshell>=0.8.0,<0.9
-openpyxl>=3.1          # XLSX export
+openpyxl>=3.1.5          # XLSX export
 numpy>=1.26           # geometry-derived quantities, AABB clash
 ifctester>=0.8        # IDS / openBIM model validation
 trimesh>=4.0          # clash narrow phase (mesh booleans) + 2D section cuts