diff --git a/zap/src/main/java/org/zaproxy/zap/ZapBootstrap.java b/zap/src/main/java/org/zaproxy/zap/ZapBootstrap.java
index 0b506195122..8b9357ba582 100644
--- a/zap/src/main/java/org/zaproxy/zap/ZapBootstrap.java
+++ b/zap/src/main/java/org/zaproxy/zap/ZapBootstrap.java
@@ -88,7 +88,11 @@ protected static void disableStdOutLog() {
         LoggerContext.getContext().getConfiguration().getRootLogger().removeAppender("stdout");
     }
 
-    private static void setLogLevel(Level level) {
+    static void setLogLevel(Level level) {
+        if (level == null) {
+            return;
+        }
+
         var config = LoggerContext.getContext().getConfiguration();
         config.getLoggerConfig("org.parosproxy.paros").setLevel(level);
         config.getLoggerConfig("org.zaproxy").setLevel(level);
diff --git a/zap/src/test/java/org/zaproxy/zap/ZapBootstrapUnitTest.java b/zap/src/test/java/org/zaproxy/zap/ZapBootstrapUnitTest.java
new file mode 100644
index 00000000000..f3d4b16700f
--- /dev/null
+++ b/zap/src/test/java/org/zaproxy/zap/ZapBootstrapUnitTest.java
@@ -0,0 +1,106 @@
+/*
+ * Zed Attack Proxy (ZAP) and its related class files.
+ *
+ * ZAP is an HTTP/HTTPS proxy for assessing web application security.
+ *
+ * Copyright 2026 The ZAP Development Team
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.zaproxy.zap;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.is;
+import static org.hamcrest.Matchers.notNullValue;
+
+import java.nio.file.Files;
+import java.util.stream.Stream;
+import org.apache.logging.log4j.Level;
+import org.apache.logging.log4j.core.LoggerContext;
+import org.apache.logging.log4j.core.config.Configuration;
+import org.apache.logging.log4j.core.config.Configurator;
+import org.apache.logging.log4j.core.config.LoggerConfig;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+/** Unit test for {@link ZapBootstrap}. */
+class ZapBootstrapUnitTest {
+
+    private static Configuration configuration;
+
+    @BeforeEach
+    void setup() throws Exception {
+        System.setProperty("zap.user.log", Files.createTempDirectory("zap-log").toString());
+        Configurator.reconfigure(
+                getClass()
+                        .getResource("/org/zaproxy/zap/resources/log4j2-home.properties")
+                        .toURI());
+        configuration = LoggerContext.getContext().getConfiguration();
+    }
+
+    @AfterEach
+    void cleanupEach() {
+        if (configuration != null) {
+            configuration.stop();
+        }
+    }
+
+    @AfterAll
+    static void cleanupAll() throws Exception {
+        Configurator.reconfigure(
+                ZapBootstrapUnitTest.class.getResource("/log4j2-test.properties").toURI());
+    }
+
+    static Stream<Level> levelProvider() {
+        return Stream.of(Level.DEBUG, Level.ERROR, Level.WARN, Level.INFO);
+    }
+
+    @ParameterizedTest
+    @MethodSource("levelProvider")
+    void shouldSetLogLevel(Level level) {
+        // Given / When
+        ZapBootstrap.setLogLevel(level);
+        // Then
+        assertLevel(getParosLoggerConfig(), level);
+        assertLevel(getZapLoggerConfig(), level);
+    }
+
+    @Test
+    void shouldNotSetNullLevel() {
+        // Given
+        configuration.getRootLogger().setLevel(Level.DEBUG);
+        // When
+        ZapBootstrap.setLogLevel(null);
+        // Then
+        assertLevel(getParosLoggerConfig(), Level.INFO);
+        assertLevel(getZapLoggerConfig(), Level.INFO);
+    }
+
+    private static LoggerConfig getZapLoggerConfig() {
+        return configuration.getLoggerConfig("org.zaproxy");
+    }
+
+    private static LoggerConfig getParosLoggerConfig() {
+        return configuration.getLoggerConfig("org.parosproxy.paros");
+    }
+
+    private static void assertLevel(LoggerConfig loggerConfig, Level level) {
+        assertThat(loggerConfig, is(notNullValue()));
+        assertThat(loggerConfig.getLevel(), is(equalTo(level)));
+    }
+}