diff --git a/opengrok-indexer/src/main/java/org/opengrok/indexer/configuration/RuntimeEnvironment.java b/opengrok-indexer/src/main/java/org/opengrok/indexer/configuration/RuntimeEnvironment.java
index 8d24bed9436..2f04697971d 100644
--- a/opengrok-indexer/src/main/java/org/opengrok/indexer/configuration/RuntimeEnvironment.java
+++ b/opengrok-indexer/src/main/java/org/opengrok/indexer/configuration/RuntimeEnvironment.java
@@ -711,7 +711,7 @@ public synchronized boolean validateUniversalCtags() {
                 ctagsLanguages.addAll(languages);
             }
 
-            ctagsFound = CtagsUtil.validate(ctagsBinary);
+            ctagsFound = CtagsUtil.isValid(ctagsBinary);
         }
 
         if (ctagsFound) {
diff --git a/opengrok-indexer/src/main/java/org/opengrok/indexer/util/CtagsUtil.java b/opengrok-indexer/src/main/java/org/opengrok/indexer/util/CtagsUtil.java
index bdea93b4354..e8b8f42bed2 100644
--- a/opengrok-indexer/src/main/java/org/opengrok/indexer/util/CtagsUtil.java
+++ b/opengrok-indexer/src/main/java/org/opengrok/indexer/util/CtagsUtil.java
@@ -25,6 +25,7 @@
 
 import org.apache.commons.lang3.SystemUtils;
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.annotations.VisibleForTesting;
 import org.opengrok.indexer.analysis.Ctags;
 import org.opengrok.indexer.analysis.Definitions;
 import org.opengrok.indexer.configuration.RuntimeEnvironment;
@@ -60,29 +61,33 @@ private CtagsUtil() {
 
     /**
      * Check that {@code ctags} program exists and is working.
-     * @param ctagsBinary name of the ctags program or path
+     * @param ctagsBinary name of the {@code ctags} program or path
      * @return true if the program works, false otherwise
      */
-    public static boolean validate(String ctagsBinary) {
+    public static boolean isValid(String ctagsBinary) {
         if (!isUniversalCtags(ctagsBinary)) {
             return false;
         }
 
-        return canProcessFiles(RuntimeEnvironment.getInstance().getSourceRootFile());
+        // The source root can be read-only. In such case, fall back to the default
+        // temporary directory as a second-best choice how to test that ctags is working.
+        return (canProcessFiles(RuntimeEnvironment.getInstance().getSourceRootFile()) ||
+                canProcessFiles(new File(System.getProperty("java.io.tmpdir"))));
     }
 
     /**
-     * Run ctags program on a known temporary file to be created under given path and see if it was possible
-     * to get some symbols.
+     * Run {@code ctags} program on a known temporary file to be created under given path
+     * and see if it was possible to get some symbols.
      * @param baseDir directory to use for storing the temporary file
      * @return true if at least one symbol was found, false otherwise
      */
-    private static boolean canProcessFiles(File baseDir) {
+    @VisibleForTesting
+    static boolean canProcessFiles(File baseDir) {
         Path inputPath;
         try {
             inputPath = File.createTempFile("ctagsValidation", ".c", baseDir).toPath();
         } catch (IOException e) {
-            LOGGER.log(Level.WARNING, "cannot create temporary file in ''{0}''", baseDir);
+            LOGGER.log(Level.WARNING, String.format("cannot create temporary file in '%s'", baseDir), e);
             return false;
         }
         final String resourceFileName = "sample.c";
diff --git a/opengrok-indexer/src/test/java/org/opengrok/indexer/util/CtagsUtilTest.java b/opengrok-indexer/src/test/java/org/opengrok/indexer/util/CtagsUtilTest.java
index f2442d2d1e9..5bef12d45d5 100644
--- a/opengrok-indexer/src/test/java/org/opengrok/indexer/util/CtagsUtilTest.java
+++ b/opengrok-indexer/src/test/java/org/opengrok/indexer/util/CtagsUtilTest.java
@@ -18,12 +18,14 @@
  */
 
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2019, Chris Fraire <cfraire@me.com>.
  */
 package org.opengrok.indexer.util;
 
 import org.junit.jupiter.api.Test;
+import org.mockito.MockedStatic;
+import org.mockito.Mockito;
 import org.opengrok.indexer.configuration.RuntimeEnvironment;
 
 import java.io.IOException;
@@ -35,6 +37,9 @@
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mockStatic;
+import static org.mockito.Mockito.times;
 
 /**
  * Represents a container for tests of {@link CtagsUtil}.
@@ -51,19 +56,40 @@ void getLanguages() {
     }
 
     @Test
-    void validate() throws IOException {
+    void testIsValid() throws IOException {
         RuntimeEnvironment env = RuntimeEnvironment.getInstance();
         Path tmpSourceRoot = Files.createTempDirectory("srcRootCtagsValidationTest");
         env.setSourceRoot(tmpSourceRoot.toString());
         assertTrue(env.getSourceRootFile().exists());
 
-        assertTrue(CtagsUtil.validate(env.getCtags()));
+        assertTrue(CtagsUtil.isValid(env.getCtags()));
 
         Files.delete(tmpSourceRoot);
     }
 
+    /**
+     * Simulate non-writable source root and verify that {@link CtagsUtil#isValid(String)} still returns true
+     * as it should fall back to default temporary directory.
+     */
     @Test
-    void testValidateWithInvalidExtraOptions() throws IOException {
+    void testIsValidNoWritableSourceRoot() throws IOException {
+        RuntimeEnvironment env = RuntimeEnvironment.getInstance();
+        Path tmpSourceRoot = Files.createTempDirectory("negativeCtagsValidationTest");
+        env.setSourceRoot(tmpSourceRoot.toString());
+        assertTrue(env.getSourceRootFile().exists());
+
+        try (MockedStatic<CtagsUtil> mocked = mockStatic(CtagsUtil.class, Mockito.CALLS_REAL_METHODS)) {
+            mocked.when(() -> CtagsUtil.canProcessFiles(env.getSourceRootFile())).thenReturn(false);
+            assertTrue(CtagsUtil.isValid(env.getCtags()));
+            mocked.verify(() -> CtagsUtil.canProcessFiles(eq(env.getSourceRootFile())),
+                    times(2)); // one extra for the lambda call above
+        }
+
+        Files.delete(tmpSourceRoot);
+    }
+
+    @Test
+    void testIsValidWithInvalidExtraOptions() throws IOException {
         RuntimeEnvironment env = RuntimeEnvironment.getInstance();
         Path tmpSourceRoot = Files.createTempDirectory("srcRootCtagsValidationTestExtraArgs");
         env.setSourceRoot(tmpSourceRoot.toString());
@@ -74,7 +100,7 @@ void testValidateWithInvalidExtraOptions() throws IOException {
         String extraOptionsAbsPath = extraOptionsPath.toAbsolutePath().toString();
 
         env.setCTagsExtraOptionsFile(extraOptionsAbsPath);
-        assertFalse(CtagsUtil.validate(env.getCtags()));
+        assertFalse(CtagsUtil.isValid(env.getCtags()));
 
         // cleanup
         env.setCTagsExtraOptionsFile(null);
diff --git a/pom.xml b/pom.xml
index 4dcbbb36b8d..ca74fbfb047 100644
--- a/pom.xml
+++ b/pom.xml
@@ -74,7 +74,7 @@ Portions Copyright (c) 2018, 2020, Chris Fraire <cfraire@me.com>.
         <maven-surefire.version>3.0.0-M5</maven-surefire.version>
         <apache-commons-lang3.version>3.13.0</apache-commons-lang3.version>
         <micrometer.version>1.11.4</micrometer.version>
-        <mockito.version>3.12.4</mockito.version>
+        <mockito.version>5.2.0</mockito.version>
         <commons-io.version>2.14.0</commons-io.version>
     </properties>