diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
index bd0d5d772..cabf5a0d4 100644
--- a/.github/workflows/pr.yml
+++ b/.github/workflows/pr.yml
@@ -101,9 +101,9 @@ jobs:
         cache-dependency-path: "**/pyproject.toml"
     - name: Collect schema files from aas-specs
       run: |
-        mkdir -p ./test/adapter/schema
-        curl -sSLf -o ./test/adapter/schema/aasJSONSchema.json https://raw.githubusercontent.com/admin-shell-io/aas-specs-metamodel/refs/tags/${{ env.X_AAS_SPECS_RELEASE_TAG }}/schemas/json/aas.json
-        curl -sSLf -o ./test/adapter/schema/aasXMLSchema.xsd https://raw.githubusercontent.com/admin-shell-io/aas-specs-metamodel/refs/tags/${{ env.X_AAS_SPECS_RELEASE_TAG }}/schemas/xml/AAS.xsd
+        mkdir -p ./test/adapter/schemas
+        curl -sSLf -o ./test/adapter/schemas/aasJSONSchema.json https://raw.githubusercontent.com/admin-shell-io/aas-specs-metamodel/refs/tags/${{ env.X_AAS_SPECS_RELEASE_TAG }}/schemas/json/aas.json
+        curl -sSLf -o ./test/adapter/schemas/aasXMLSchema.xsd https://raw.githubusercontent.com/admin-shell-io/aas-specs-metamodel/refs/tags/${{ env.X_AAS_SPECS_RELEASE_TAG }}/schemas/xml/AAS.xsd
     - name: Install Python dependencies
       run: |
         python -m pip install --upgrade pip
@@ -112,6 +112,9 @@ jobs:
       run: |
         python test/_helper/setup_testdb.py -u "admin" -p "$COUCHDB_ADMIN_PASSWORD"
     - name: Test with coverage + unittest
+      env:
+        # Fail instead of silently skipping if the schema files above are missing (see test_helpers.py).
+        REQUIRE_SCHEMA_TESTS: "1"
       run: |
         python -m coverage run --source=basyx -m unittest
     - name: Report test coverage
diff --git a/sdk/test/_helper/test_helpers.py b/sdk/test/_helper/test_helpers.py
index 3633519a1..71975d4d8 100644
--- a/sdk/test/_helper/test_helpers.py
+++ b/sdk/test/_helper/test_helpers.py
@@ -7,6 +7,7 @@
 
 import base64
 import configparser
+import os
 import os.path
 import urllib.error
 import urllib.request
@@ -20,6 +21,12 @@
 )
 
 
+# By default, the schema validation tests are skipped when the AAS schema files are missing, so that a plain local
+# `python -m unittest` run doesn't require downloading them first. Set this environment variable to "1"/"true"
+# (e.g. in CI) to instead make those tests fail if the files are missing, so a broken download can't silently cause
+# the tests to be skipped without anyone noticing.
+REQUIRE_SCHEMAS = os.environ.get("REQUIRE_SCHEMA_TESTS", "false").lower() in {"1", "true", "yes"}
+
 # Check if CouchDB database is available. Otherwise, skip tests.
 try:
     request = urllib.request.Request(
diff --git a/sdk/test/adapter/json/test_json_serialization.py b/sdk/test/adapter/json/test_json_serialization.py
index e53cf6041..c727ba267 100644
--- a/sdk/test/adapter/json/test_json_serialization.py
+++ b/sdk/test/adapter/json/test_json_serialization.py
@@ -25,6 +25,8 @@
 )
 from jsonschema import validate  # type: ignore
 
+from test._helper.test_helpers import REQUIRE_SCHEMAS
+
 JSON_SCHEMA_FILE = os.path.join(
     os.path.dirname(__file__), "../schemas/aasJSONSchema.json"
 )
@@ -72,6 +74,10 @@ class JsonSerializationSchemaTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         if not os.path.exists(JSON_SCHEMA_FILE):
+            if REQUIRE_SCHEMAS:
+                raise RuntimeError(
+                    f"REQUIRE_SCHEMA_TESTS is set, but the JSON Schema does not exist at {JSON_SCHEMA_FILE}"
+                )
             raise unittest.SkipTest(
                 f"JSON Schema does not exist at {JSON_SCHEMA_FILE}, skipping test"
             )
diff --git a/sdk/test/adapter/xml/test_xml_serialization.py b/sdk/test/adapter/xml/test_xml_serialization.py
index 625cd9943..0b5616743 100644
--- a/sdk/test/adapter/xml/test_xml_serialization.py
+++ b/sdk/test/adapter/xml/test_xml_serialization.py
@@ -18,6 +18,8 @@
 )
 from lxml import etree
 
+from test._helper.test_helpers import REQUIRE_SCHEMAS
+
 XML_SCHEMA_FILE = os.path.join(os.path.dirname(__file__), "../schemas/aasXMLSchema.xsd")
 
 
@@ -63,6 +65,10 @@ class XMLSerializationSchemaTest(unittest.TestCase):
     @classmethod
     def setUpClass(cls):
         if not os.path.exists(XML_SCHEMA_FILE):
+            if REQUIRE_SCHEMAS:
+                raise RuntimeError(
+                    f"REQUIRE_SCHEMA_TESTS is set, but the XSD schema does not exist at {XML_SCHEMA_FILE}"
+                )
             raise unittest.SkipTest(
                 f"XSD schema does not exist at {XML_SCHEMA_FILE}, skipping test"
             )