diff --git a/osbuild/util/sbom/spdx.py b/osbuild/util/sbom/spdx.py
index de9daead..541452b3 100644
--- a/osbuild/util/sbom/spdx.py
+++ b/osbuild/util/sbom/spdx.py
@@ -53,7 +53,13 @@ class SpdxLicenseExpressionCreator:
 
         If the license-expression package is not available, the license string is always wrapped in an
         ExtractedLicensingInfo object.
+
+        License strings that are already SPDX license ref IDs are returned as is.
         """
+        if license_str.startswith("LicenseRef-"):
+            # The license string is already an SPDX license ref ID.
+            return license_str
+
         if self._spdx_licensing is None:
             return self._to_extracted_license_info(license_str)
 
diff --git a/test/mod/test_util_sbom_spdx.py b/test/mod/test_util_sbom_spdx.py
index 6d237df0..6ea904a6 100644
--- a/test/mod/test_util_sbom_spdx.py
+++ b/test/mod/test_util_sbom_spdx.py
@@ -27,6 +27,9 @@ def test_spdxlicenseexpressionfactory_license_expression_availability(licensing_
         lf = SpdxLicenseExpressionCreator()
         license_expression = lf.ensure_license_expression("MIT")
 
+        license_expression2 = lf.ensure_license_expression("LicenseRef-123")
+        assert license_expression2 == "LicenseRef-123"
+
         if licensing_available:
             assert mocked_licensing is not None
             # The license string should be a SPDX license expression string.