diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileSnapshotTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileSnapshotTest.java
index 902416bdf..07b1bc789 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileSnapshotTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/FileSnapshotTest.java
@@ -42,6 +42,7 @@
  */
 package org.eclipse.jgit.internal.storage.file;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
@@ -98,6 +99,27 @@ public void testActuallyIsModifiedTrivial() throws Exception {
 		assertTrue(save.isModified(f1));
 	}
 
+	/**
+	 * Check that file is modified by looking at its size.
+	 *
+	 * @throws Exception
+	 */
+	@Test
+	public void tesIsModifiedBySameLastModifiedAndDifferentSize() throws Exception {
+		File f1 = createFile("foo", "lorem".getBytes());
+		File f2 = createFile("bar", "lorem ipsum".getBytes());
+
+		f1.setLastModified(f2.lastModified()); // Make sure f1 and f2 have the same lastModified
+		FileSnapshot save = FileSnapshot.save(f1);
+
+		// Make sure that the modified and read timestamps are far enough, so that
+		// check is done by size
+		Thread.sleep(3000L);
+
+		assertEquals(save.lastModified(), f2.lastModified());
+		assertTrue(save.isModified(f2));
+	}
+
 	/**
 	 * Create a file, wait long enough and verify that it has not been modified.
 	 * 3.5 seconds mean any difference between file system timestamp and system
@@ -152,10 +174,22 @@ private File createFile(String string) throws IOException {
 		return f;
 	}
 
+	private File createFile(String string, byte[] content) throws IOException {
+		File f = createFile(string);
+		append(f, content);
+		return f;
+	}
+
 	private static void append(File f, byte b) throws IOException {
+		append(f, new byte[] { b });
+	}
+
+	private static void append(File f, byte[] content) throws IOException {
 		FileOutputStream os = new FileOutputStream(f, true);
 		try {
-			os.write(b);
+			for (byte b : content) {
+				os.write(b);
+			}
 		} finally {
 			os.close();
 		}
diff --git a/org.eclipse.jgit/.settings/.api_filters b/org.eclipse.jgit/.settings/.api_filters
index d259fc85f..fe83211eb 100644
--- a/org.eclipse.jgit/.settings/.api_filters
+++ b/org.eclipse.jgit/.settings/.api_filters
@@ -22,4 +22,12 @@
             </message_arguments>
         </filter>
     </resource>
+    <resource path="src/org/eclipse/jgit/util/FS.java" type="org.eclipse.jgit.util.FS">
+        <filter id="1142947843">
+            <message_arguments>
+                <message_argument value="4.5.6"/>
+                <message_argument value="fileAttributes(File)"/>
+            </message_arguments>
+        </filter>
+    </resource>
 </component>
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java
index 8926d7930..fbd1dbf69 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/FileSnapshot.java
@@ -45,6 +45,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.util.Date;
@@ -69,6 +70,13 @@
  * file is less than 3 seconds ago.
  */
 public class FileSnapshot {
+	/**
+	 * An unknown file size.
+	 *
+	 * This value is used when a comparison needs to happen purely on the lastUpdate.
+	 */
+	public static final long UNKNOWN_SIZE = -1;
+
 	/**
 	 * A FileSnapshot that is considered to always be modified.
 	 * <p>
@@ -76,7 +84,7 @@ public class FileSnapshot {
 	 * file, but only after {@link #isModified(File)} gets invoked. The returned
 	 * snapshot contains only invalid status information.
 	 */
-	public static final FileSnapshot DIRTY = new FileSnapshot(-1, -1);
+	public static final FileSnapshot DIRTY = new FileSnapshot(-1, -1, UNKNOWN_SIZE);
 
 	/**
 	 * A FileSnapshot that is clean if the file does not exist.
@@ -85,7 +93,7 @@ public class FileSnapshot {
 	 * file to be clean. {@link #isModified(File)} will return false if the file
 	 * path does not exist.
 	 */
-	public static final FileSnapshot MISSING_FILE = new FileSnapshot(0, 0) {
+	public static final FileSnapshot MISSING_FILE = new FileSnapshot(0, 0, 0) {
 		@Override
 		public boolean isModified(File path) {
 			return FS.DETECTED.exists(path);
@@ -105,12 +113,16 @@ public boolean isModified(File path) {
 	public static FileSnapshot save(File path) {
 		long read = System.currentTimeMillis();
 		long modified;
+		long size;
 		try {
-			modified = FS.DETECTED.lastModified(path);
+			BasicFileAttributes fileAttributes = FS.DETECTED.fileAttributes(path);
+			modified = fileAttributes.lastModifiedTime().toMillis();
+			size = fileAttributes.size();
 		} catch (IOException e) {
 			modified = path.lastModified();
+			size = path.length();
 		}
-		return new FileSnapshot(read, modified);
+		return new FileSnapshot(read, modified, size);
 	}
 
 	/**
@@ -126,7 +138,7 @@ public static FileSnapshot save(File path) {
 	 */
 	public static FileSnapshot save(long modified) {
 		final long read = System.currentTimeMillis();
-		return new FileSnapshot(read, modified);
+		return new FileSnapshot(read, modified, -1);
 	}
 
 	/** Last observed modification time of the path. */
@@ -138,10 +150,16 @@ public static FileSnapshot save(long modified) {
 	/** True once {@link #lastRead} is far later than {@link #lastModified}. */
 	private boolean cannotBeRacilyClean;
 
-	private FileSnapshot(long read, long modified) {
+	/** Underlying file-system size in bytes.
+	 *
+	 * When set to {@link #UNKNOWN_SIZE} the size is not considered for modification checks. */
+	private final long size;
+
+	private FileSnapshot(long read, long modified, long size) {
 		this.lastRead = read;
 		this.lastModified = modified;
 		this.cannotBeRacilyClean = notRacyClean(read);
+		this.size = size;
 	}
 
 	/**
@@ -151,6 +169,13 @@ public long lastModified() {
 		return lastModified;
 	}
 
+	/**
+	 * @return file size in bytes of last snapshot update
+	 */
+	public long size() {
+		return size;
+	}
+
 	/**
 	 * Check if the path may have been modified since the snapshot was saved.
 	 *
@@ -160,12 +185,16 @@ public long lastModified() {
 	 */
 	public boolean isModified(File path) {
 		long currLastModified;
+		long currSize;
 		try {
-			currLastModified = FS.DETECTED.lastModified(path);
+			BasicFileAttributes fileAttributes = FS.DETECTED.fileAttributes(path);
+			currLastModified = fileAttributes.lastModifiedTime().toMillis();
+			currSize = fileAttributes.size();
 		} catch (IOException e) {
 			currLastModified = path.lastModified();
+			currSize = path.length();
 		}
-		return isModified(currLastModified);
+		return (currSize != UNKNOWN_SIZE && currSize != size) || isModified(currLastModified);
 	}
 
 	/**
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
index e1fd1cb88..530b1d4bc 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
@@ -52,6 +52,7 @@
 import java.io.OutputStream;
 import java.io.PrintStream;
 import java.nio.charset.Charset;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.text.MessageFormat;
@@ -417,6 +418,19 @@ public FS setUserHome(File path) {
 	 */
 	public abstract boolean retryFailedLockFileCommit();
 
+	/**
+	 * Return all the attributes of a file, without following symbolic links.
+	 *
+	 * @param file
+	 * @return {@link BasicFileAttributes} of the file
+	 * @throws IOException in case of any I/O errors accessing the file
+	 *
+	 * @since 4.5.6
+	 */
+	public BasicFileAttributes fileAttributes(File file) throws IOException {
+		return FileUtils.fileAttributes(file);
+	}
+
 	/**
 	 * Determine the user's home directory (location where preferences are).
 	 *
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/FileUtils.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/FileUtils.java
index aa101f73f..88b1f9ea0 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/FileUtils.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/FileUtils.java
@@ -564,6 +564,19 @@ static long lastModified(File file) throws IOException {
 				.toMillis();
 	}
 
+	/**
+	 * Return all the attributes of a file, without following symbolic links.
+	 *
+	 * @param file
+	 * @return {@link BasicFileAttributes} of the file
+	 * @throws IOException in case of any I/O errors accessing the file
+	 *
+	 * @since 4.5.6
+	 */
+	static BasicFileAttributes fileAttributes(File file) throws IOException {
+		return Files.readAttributes(file.toPath(), BasicFileAttributes.class, LinkOption.NOFOLLOW_LINKS);
+	}
+
 	/**
 	 * @param file
 	 * @param time