diff --git a/services/api/requirements.in b/services/api/requirements.in
index 09452252..17dabfd9 100644
--- a/services/api/requirements.in
+++ b/services/api/requirements.in
@@ -61,7 +61,7 @@ pyhanko>=0.36.2            # PAdES certificate-based PDF digital signatures (esi
 pypdf>=6.16.1           # CVE-2026-84310/-84311 floor (-84309 fixed in 6.16.0, so 6.16.1 clears all three; was 6.15.0 for -71852/-71870, 6.14.2 for -59935/-59936); contract/spec text extraction for the review engine (review.py)
 defusedxml>=0.7.1        # XXE / billion-laughs hardening for untrusted CityGML parsing (citygml.py)
 pyarrow>=16.0          # columnar Parquet export of the model element set (model_query.to_parquet)
-signxml>=3.2           # SAML 2.0 assertion XML-DSig signature verification (saml.py)
+signxml>=5.1.0           # SAML 2.0 assertion XML-DSig signature verification (saml.py)
 ezdxf>=1.1             # DXF quantity takeoff — 2D CAD estimating (dxf_takeoff.py); MIT, pure-Python
 
 # --- caching ---