diff --git a/runtime/tests/org.eclipse.core.tests.harness/META-INF/MANIFEST.MF b/runtime/tests/org.eclipse.core.tests.harness/META-INF/MANIFEST.MF
index 4e515734337..ed67d89930b 100644
--- a/runtime/tests/org.eclipse.core.tests.harness/META-INF/MANIFEST.MF
+++ b/runtime/tests/org.eclipse.core.tests.harness/META-INF/MANIFEST.MF
@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: Eclipse Core Tests Harness
 Bundle-SymbolicName: org.eclipse.core.tests.harness;singleton:=true
-Bundle-Version: 3.17.400.qualifier
+Bundle-Version: 3.17.500.qualifier
 Bundle-Vendor: Eclipse.org
 Export-Package: org.eclipse.core.tests.harness;version="2.0",
  org.eclipse.core.tests.harness.session,
diff --git a/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/CustomSessionConfiguration.java b/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/CustomSessionConfiguration.java
index 9307a8d9358..3a918accf50 100644
--- a/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/CustomSessionConfiguration.java
+++ b/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/CustomSessionConfiguration.java
@@ -72,4 +72,15 @@ public interface CustomSessionConfiguration extends SessionCustomization {
 	 */
 	public CustomSessionConfiguration setReadOnly();
 
+	/**
+	 * Sets the given config value for the application configuration via the ini. If
+	 * the value is null, the key will be removed from the ini.
+	 *
+	 * @param key   the key to define
+	 * @param value the value to set to the key or {@code null} to remove the key
+	 *
+	 * @return this
+	 */
+	public CustomSessionConfiguration setConfigIniValue(String key, String value);
+
 }
diff --git a/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/RemoteTestExecutor.java b/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/RemoteTestExecutor.java
index 899bf5153f0..452382115ca 100644
--- a/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/RemoteTestExecutor.java
+++ b/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/RemoteTestExecutor.java
@@ -66,7 +66,7 @@ void executeRemotely(String testClass, String testMethod, boolean shouldFail) th
 				throw new CoreException(status);
 			}
 			if (!collector.didTestFinish()) {
-				throw new Exception("session test did not run: " + descriptor);
+				throw new Exception("session test did not run: " + descriptor + "\n" + collector.stackTrace);
 			}
 			if (!collector.wasTestSuccessful()) {
 				throw collector.getError();
diff --git a/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/customization/CustomSessionConfigurationDummy.java b/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/customization/CustomSessionConfigurationDummy.java
index c6b7fdd692d..095d42421f6 100644
--- a/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/customization/CustomSessionConfigurationDummy.java
+++ b/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/customization/CustomSessionConfigurationDummy.java
@@ -63,4 +63,9 @@ public CustomSessionConfiguration addBundle(Bundle bundle) {
 		return this;
 	}
 
+	@Override
+	public CustomSessionConfiguration setConfigIniValue(String key, String value) {
+		return this;
+	}
+
 }
diff --git a/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/customization/CustomSessionConfigurationImpl.java b/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/customization/CustomSessionConfigurationImpl.java
index bff7694721d..09b56296a1b 100644
--- a/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/customization/CustomSessionConfigurationImpl.java
+++ b/runtime/tests/org.eclipse.core.tests.harness/src/org/eclipse/core/tests/harness/session/customization/CustomSessionConfigurationImpl.java
@@ -20,7 +20,9 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Collection;
+import java.util.HashMap;
 import java.util.LinkedHashSet;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Properties;
@@ -50,6 +52,7 @@ public class CustomSessionConfigurationImpl implements CustomSessionConfiguratio
 
 	private final Collection<BundleReference> bundleReferences = new LinkedHashSet<>();
 	private Path configurationDirectory;
+	private final Map<String, String> configIniValues = new HashMap<>();
 	private boolean readOnly = false;
 	private boolean cascaded = false;
 	private boolean firstExecutedSession = true;
@@ -141,6 +144,16 @@ public CustomSessionConfiguration setReadOnly() {
 		return this;
 	}
 
+	@Override
+	public CustomSessionConfiguration setConfigIniValue(String key, String value) {
+		if (value == null) {
+			configIniValues.remove(key);
+		} else {
+			configIniValues.put(key, value);
+		}
+		return this;
+	}
+
 	@Override
 	public CustomSessionConfiguration setConfigurationDirectory(Path configurationDirectory) {
 		Objects.requireNonNull(configurationDirectory);
@@ -212,6 +225,9 @@ private void createOrRefreshConfigIni() throws IOException {
 			contents.put(PROP_SHARED_CONFIG_AREA, Platform.getConfigurationLocation().getURL().toExternalForm());
 		}
 		contents.put(PROP_CONFIG_AREA_READ_ONLY, Boolean.valueOf(readOnly).toString());
+		for (Map.Entry<String, String> entry : configIniValues.entrySet()) {
+			contents.put(entry.getKey(), entry.getValue());
+		}
 		// save the properties
 		Path configINI = getConfigurationDirectory().resolve("config.ini");
 		try (OutputStream out = Files.newOutputStream(configINI)) {