diff --git a/pyproject.toml b/pyproject.toml
index 016dbbb..c8b0f66 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,7 +23,7 @@ dependencies = [
     "xmlsec", # tested with 1.3.16
     "asn1crypto", # tested with 1.5.1
     "certvalidator", # tested with 0.11.1
-    "saxonche", # tested with 12.9.0
+    "saxonche==13.0.0", # tested with 12.9.0
     "dnspython==2.*", # tested with 2.8.0
 ]