diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/RefUpdateTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/RefUpdateTest.java
index 757ebb298..b2fae316c 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/RefUpdateTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/RefUpdateTest.java
@@ -45,8 +45,9 @@
 
 package org.eclipse.jgit.internal.storage.file;
 
-import static org.eclipse.jgit.lib.Constants.CHARSET;
 import static org.eclipse.jgit.junit.Assert.assertEquals;
+import static org.eclipse.jgit.lib.Constants.CHARSET;
+import static org.eclipse.jgit.lib.Constants.LOCK_SUFFIX;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -819,11 +820,11 @@ public class RefUpdateTest extends SampleDataRepositoryTestCase {
 			// Check that the involved refs are the same despite the failure
 			assertExists(false, toName);
 			if (!toLock.equals(toName))
-				assertExists(false, toName + ".lock");
-			assertExists(true, toLock + ".lock");
+				assertExists(false, toName + LOCK_SUFFIX);
+			assertExists(true, toLock + LOCK_SUFFIX);
 			if (!toLock.equals(fromName))
-				assertExists(false, "logs/" + fromName + ".lock");
-			assertExists(false, "logs/" + toName + ".lock");
+				assertExists(false, "logs/" + fromName + LOCK_SUFFIX);
+			assertExists(false, "logs/" + toName + LOCK_SUFFIX);
 			assertEquals(oldHeadId, db.resolve(Constants.HEAD));
 			assertEquals(oldfromId, db.resolve(fromName));
 			assertNull(db.resolve(toName));
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileRepository.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileRepository.java
index c3dad6162..5ced68646 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileRepository.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileRepository.java
@@ -56,7 +56,6 @@ import java.util.HashSet;
 import java.util.Locale;
 import java.util.Objects;
 import java.util.Set;
-import java.util.concurrent.locks.ReentrantLock;
 
 import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.api.errors.JGitInternalException;
@@ -125,7 +124,7 @@ public class FileRepository extends Repository {
 	private final RefDatabase refs;
 	private final ObjectDirectory objectDatabase;
 
-	private final ReentrantLock snapshotLock = new ReentrantLock();
+	private final Object snapshotLock = new Object();
 
 	// protected by snapshotLock
 	private FileSnapshot snapshot;
@@ -553,29 +552,23 @@ public class FileRepository extends Repository {
 		}
 
 		File indexFile = getIndexFile();
-		snapshotLock.lock();
-		try {
+		synchronized (snapshotLock) {
 			if (snapshot == null) {
 				snapshot = FileSnapshot.save(indexFile);
-			} else if (snapshot.isModified(indexFile)) {
-				snapshotLock.unlock();
-				notifyIndexChanged(false);
+				return;
 			}
-		} finally {
-			if (snapshotLock.isHeldByCurrentThread()) {
-				snapshotLock.unlock();
+			if (!snapshot.isModified(indexFile)) {
+				return;
 			}
 		}
+		notifyIndexChanged(false);
 	}
 
 	/** {@inheritDoc} */
 	@Override
 	public void notifyIndexChanged(boolean internal) {
-		snapshotLock.lock();
-		try {
+		synchronized (snapshotLock) {
 			snapshot = FileSnapshot.save(getIndexFile());
-		} finally {
-			snapshotLock.unlock();
 		}
 		fireEvent(new IndexChangedEvent(internal));
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/LockFile.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/LockFile.java
index a11e4ffdf..da9a050bc 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/LockFile.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/LockFile.java
@@ -44,6 +44,8 @@
 
 package org.eclipse.jgit.internal.storage.file;
 
+import static org.eclipse.jgit.lib.Constants.LOCK_SUFFIX;
+
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
@@ -74,7 +76,6 @@ import org.eclipse.jgit.util.FileUtils;
  * name.
  */
 public class LockFile {
-	static final String SUFFIX = ".lock"; //$NON-NLS-1$
 
 	/**
 	 * Unlock the given file.
@@ -106,14 +107,15 @@ public class LockFile {
 	 * @return lock file
 	 */
 	static File getLockFile(File file) {
-		return new File(file.getParentFile(), file.getName() + SUFFIX);
+		return new File(file.getParentFile(),
+				file.getName() + LOCK_SUFFIX);
 	}
 
 	/** Filter to skip over active lock files when listing a directory. */
 	static final FilenameFilter FILTER = new FilenameFilter() {
 		@Override
 		public boolean accept(File dir, String name) {
-			return !name.endsWith(SUFFIX);
+			return !name.endsWith(LOCK_SUFFIX);
 		}
 	};
 
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ReflogWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ReflogWriter.java
index b366eafe2..495c75236 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ReflogWriter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/ReflogWriter.java
@@ -46,6 +46,7 @@
 package org.eclipse.jgit.internal.storage.file;
 
 import static org.eclipse.jgit.lib.Constants.HEAD;
+import static org.eclipse.jgit.lib.Constants.LOCK_SUFFIX;
 import static org.eclipse.jgit.lib.Constants.R_HEADS;
 import static org.eclipse.jgit.lib.Constants.R_NOTES;
 import static org.eclipse.jgit.lib.Constants.R_REFS;
@@ -84,7 +85,7 @@ public class ReflogWriter {
 	 * @return the name of the ref's lock ref.
 	 */
 	public static String refLockFor(String name) {
-		return name + LockFile.SUFFIX;
+		return name + LOCK_SUFFIX;
 	}
 
 	private final RefDirectory refdb;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java
index a119480ea..ecebd5408 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java
@@ -691,6 +691,13 @@ public final class Constants {
 	public static final ObjectId EMPTY_BLOB_ID = ObjectId
 			.fromString("e69de29bb2d1d6434b8b29ae775ad8c2e48c5391");
 
+	/**
+	 * Suffix of lock file name
+	 *
+	 * @since 5.0
+	 */
+	public static final String LOCK_SUFFIX = ".lock"; //$NON-NLS-1$
+
 	private Constants() {
 		// Hide the default constructor
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java
index 5fec5aadf..d73c05e24 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java
@@ -48,6 +48,8 @@
 
 package org.eclipse.jgit.lib;
 
+import static org.eclipse.jgit.lib.Constants.LOCK_SUFFIX;
+
 import java.io.BufferedOutputStream;
 import java.io.File;
 import java.io.FileNotFoundException;
@@ -1368,10 +1370,12 @@ public abstract class Repository implements AutoCloseable {
 	 */
 	public static boolean isValidRefName(String refName) {
 		final int len = refName.length();
-		if (len == 0)
+		if (len == 0) {
 			return false;
-		if (refName.endsWith(".lock")) //$NON-NLS-1$
+		}
+		if (refName.endsWith(LOCK_SUFFIX)) {
 			return false;
+		}
 
 		// Refs may be stored as loose files so invalid paths
 		// on the local system must also be invalid refs.
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/TransportSftp.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/TransportSftp.java
index d8f3a12bf..f129ba34d 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/TransportSftp.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/TransportSftp.java
@@ -43,6 +43,8 @@
 
 package org.eclipse.jgit.transport;
 
+import static org.eclipse.jgit.lib.Constants.LOCK_SUFFIX;
+
 import java.io.BufferedReader;
 import java.io.FileNotFoundException;
 import java.io.IOException;
@@ -344,7 +346,7 @@ public class TransportSftp extends SshTransport implements WalkTransport {
 
 		@Override
 		void writeFile(String path, byte[] data) throws IOException {
-			final String lock = path + ".lock"; //$NON-NLS-1$
+			final String lock = path + LOCK_SUFFIX;
 			try {
 				super.writeFile(lock, data);
 				try {