diff --git a/tools/server-spring/src/main/java/org/eclipse/rdf4j/http/server/repository/transaction/TransactionStartController.java b/tools/server-spring/src/main/java/org/eclipse/rdf4j/http/server/repository/transaction/TransactionStartController.java
index 36fe12ebd0d..69b0dfbd4bc 100644
--- a/tools/server-spring/src/main/java/org/eclipse/rdf4j/http/server/repository/transaction/TransactionStartController.java
+++ b/tools/server-spring/src/main/java/org/eclipse/rdf4j/http/server/repository/transaction/TransactionStartController.java
@@ -83,12 +83,14 @@ private ModelAndView startTransaction(Repository repository, HttpServletRequest
 
 		// process legacy isolation level param for backward compatibility with older clients
 		final String isolationLevelString = request.getParameter(Protocol.ISOLATION_LEVEL_PARAM_NAME);
-		final IRI level = Values.iri(isolationLevelString);
+		if (isolationLevelString != null) {
+			final IRI level = Values.iri(isolationLevelString);
 
-		for (IsolationLevel standardLevel : IsolationLevels.values()) {
-			if (standardLevel.getName().equals(level.getLocalName())) {
-				isolationLevel[0] = standardLevel;
-				break;
+			for (IsolationLevel standardLevel : IsolationLevels.values()) {
+				if (standardLevel.getName().equals(level.getLocalName())) {
+					isolationLevel[0] = standardLevel;
+					break;
+				}
 			}
 		}
 
diff --git a/tools/server/pom.xml b/tools/server/pom.xml
index 93d3764494e..b2c967ec8db 100644
--- a/tools/server/pom.xml
+++ b/tools/server/pom.xml
@@ -65,6 +65,12 @@
 			<artifactId>jcl-over-slf4j</artifactId>
 			<scope>runtime</scope>
 		</dependency>
+		<dependency>
+			<groupId>${project.groupId}</groupId>
+			<artifactId>rdf4j-repository-manager</artifactId>
+			<version>${project.version}</version>
+			<scope>test</scope>
+		</dependency>
 		<dependency>
 			<groupId>org.junit.vintage</groupId>
 			<artifactId>junit-vintage-engine</artifactId>
diff --git a/tools/server/src/test/java/org/eclipse/rdf4j/http/server/TestServer.java b/tools/server/src/test/java/org/eclipse/rdf4j/http/server/TestServer.java
index 6fc216ae51a..c44d18c49f2 100644
--- a/tools/server/src/test/java/org/eclipse/rdf4j/http/server/TestServer.java
+++ b/tools/server/src/test/java/org/eclipse/rdf4j/http/server/TestServer.java
@@ -21,8 +21,8 @@
 import org.eclipse.rdf4j.repository.RepositoryException;
 import org.eclipse.rdf4j.repository.config.RepositoryConfig;
 import org.eclipse.rdf4j.repository.config.RepositoryConfigException;
-import org.eclipse.rdf4j.repository.config.RepositoryConfigUtil;
 import org.eclipse.rdf4j.repository.http.HTTPRepository;
+import org.eclipse.rdf4j.repository.manager.RemoteRepositoryManager;
 import org.eclipse.rdf4j.repository.manager.SystemRepository;
 import org.eclipse.rdf4j.repository.sail.config.SailRepositoryConfig;
 import org.eclipse.rdf4j.sail.inferencer.fc.config.SchemaCachingRDFSInferencerConfig;
@@ -98,30 +98,25 @@ public void stop() throws Exception {
 	}
 
 	private void createTestRepositories() throws RepositoryException, RepositoryConfigException {
-		Repository systemRep = new HTTPRepository(Protocol.getRepositoryLocation(SERVER_URL, SystemRepository.ID));
-
+		RemoteRepositoryManager manager = RemoteRepositoryManager.getInstance(SERVER_URL);
 		// create a (non-inferencing) memory store
 		MemoryStoreConfig memStoreConfig = new MemoryStoreConfig();
 		SailRepositoryConfig sailRepConfig = new SailRepositoryConfig(memStoreConfig);
 		RepositoryConfig repConfig = new RepositoryConfig(TEST_REPO_ID, sailRepConfig);
-
-		RepositoryConfigUtil.updateRepositoryConfigs(systemRep, repConfig);
+		manager.addRepositoryConfig(repConfig);
 
 		// create an inferencing memory store
 		SchemaCachingRDFSInferencerConfig inferMemStoreConfig = new SchemaCachingRDFSInferencerConfig(
 				new MemoryStoreConfig());
 		sailRepConfig = new SailRepositoryConfig(inferMemStoreConfig);
 		repConfig = new RepositoryConfig(TEST_INFERENCE_REPO_ID, sailRepConfig);
-
-		RepositoryConfigUtil.updateRepositoryConfigs(systemRep, repConfig);
+		manager.addRepositoryConfig(repConfig);
 
 		// create memory store with shacl support
 		ShaclSailConfig shaclConfig = new ShaclSailConfig(new MemoryStoreConfig());
 		sailRepConfig = new SailRepositoryConfig(shaclConfig);
 		repConfig = new RepositoryConfig(TEST_SHACL_REPO_ID, sailRepConfig);
-
-		RepositoryConfigUtil.updateRepositoryConfigs(systemRep, repConfig);
-
+		manager.addRepositoryConfig(repConfig);
 	}
 
 	static class PropertiesReader {