diff --git a/var/spack/repos/builtin/packages/xerces-c/package.py b/var/spack/repos/builtin/packages/xerces-c/package.py
index b31facf98ff..b31bb5525e5 100644
--- a/var/spack/repos/builtin/packages/xerces-c/package.py
+++ b/var/spack/repos/builtin/packages/xerces-c/package.py
@@ -31,7 +31,7 @@ class XercesC(AutotoolsPackage):
     variant(
         "cxxstd",
         default="default",
-        values=("default", "98", "11", "14", "17"),
+        values=("default", "98", "11", "14", "17", "20"),
         multi=False,
         description="Use the specified C++ standard when building",
     )