diff --git a/src/wp-admin/includes/post.php b/src/wp-admin/includes/post.php
index d230667..2a27cf8 100644
--- a/src/wp-admin/includes/post.php
+++ b/src/wp-admin/includes/post.php
@@ -1544,6 +1544,15 @@ function wp_create_post_autosave( $post_data ) {
 			return 0;
 		}
 
+		/**
+		 * Fires before an autosave is stored.
+		 *
+		 * @since 4.1.0
+		 *
+		 * @param Object $new_autosave Post object - the autosave that is about to be saved.
+		 */
+		do_action( '_wp_creating_autosave', $new_autosave );
+
 		return wp_update_post( $new_autosave );
 	}
 
diff --git a/src/wp-admin/includes/revision.php b/src/wp-admin/includes/revision.php
index 151cd64..17be3d2 100644
--- a/src/wp-admin/includes/revision.php
+++ b/src/wp-admin/includes/revision.php
@@ -92,7 +92,7 @@ function wp_get_revision_ui_diff( $post, $compare_from, $compare_to ) {
 			);
 		}
 	}
-	return $return;
+	return apply_filters( 'wp_get_revision_ui_diff', $return, $compare_from, $compare_to );
 }
 
 /**
diff --git a/src/wp-includes/revision.php b/src/wp-includes/revision.php
index 45e436f..59aff6c 100644
--- a/src/wp-includes/revision.php
+++ b/src/wp-includes/revision.php
@@ -133,9 +133,26 @@ function wp_save_post_revision( $post_id ) {
 					break;
 				}
 			}
+
+			/**
+			 * Filter whether a post has changed.
+			 *
+			 * By default a revision is saved only if one of the revisioned fields has changed.
+			 * This filter allows for additional checks to determine if there were changes.
+			 *
+			 * @since 4.1.0
+			 *
+			 * @param bool $post_has_changed Whether the post has changed.
+			 * @param int  $last_revision    ID of the last revision.
+			 * @param int  $post             Post ID.
+			 *
+			 */
+			$post_has_changed = (bool) apply_filters( 'wp_save_post_revision_additional_check_for_changes', $post_has_changed, $last_revision, $post );
+
 			//don't save revision if post unchanged
-			if( ! $post_has_changed )
+			if( ! $post_has_changed ) {
 				return;
+			}
 		}
 	}
 
diff --git a/tests/phpunit/tests/post/revisions.php b/tests/phpunit/tests/post/revisions.php
index aa3819a..9b0013f 100644
--- a/tests/phpunit/tests/post/revisions.php
+++ b/tests/phpunit/tests/post/revisions.php
@@ -367,4 +367,181 @@ class Tests_Post_Revisions extends WP_UnitTestCase {
 		$this->assertEquals( 100, $ok );
 		$this->assertEquals( 0, $reversed );
 	}
+
+	/**
+	 * Test the revisions system for storage of meta values
+	 * @ticket 20564
+	 */
+	function test_revisions_stores_meta_values() {
+		// Set up a new post
+		$original_post_id = $post_id = $this->factory->post->create();
+		// And update to store an initial revision
+		wp_update_post( array( 'post_content'	=> 'some initial content', 'ID' => $post_id ) );
+
+		// One revision so far
+		$revisions = wp_get_post_revisions( $post_id );
+		$this->assertCount( 1, $revisions );
+		/**
+		 * First set up a meta value
+		 */
+
+		// Store a custom meta value, which is not revisioned by default
+		update_post_meta( $post_id, 'meta_revision_test', 'original' );
+
+		// Update the post, storing a revision
+		wp_update_post( array( 'post_content'	=> 'some more content', 'ID' => $post_id ) );
+
+		$revisions = wp_get_post_revisions( $post_id );
+		$this->assertCount( 2, $revisions );
+
+
+		//  Next, store some updated meta values for the same key
+		update_post_meta( $post_id, 'meta_revision_test', 'update1' );
+
+		// Save the post, changing content to force a revision
+		wp_update_post( array( 'post_content'	=> 'some updated content', 'ID' => $post_id ) );
+
+		$revisions = wp_get_post_revisions( $post_id );
+		$this->assertCount( 3, $revisions );
+
+
+		/**
+		 * Now restore the original revision
+		 */
+
+		// Restore the previous revision
+		$revisions = (Array)wp_get_post_revisions( $post_id );
+		// Go back two to load the previous revision
+		array_shift( $revisions );
+		$last_revision = array_shift( $revisions );
+		// Restore!
+		wp_restore_post_revision( $last_revision->ID );
+
+		wp_update_post( array( 'ID' => $post_id ) );
+		$revisions = wp_get_post_revisions( $post_id );
+		$this->assertCount( 4, $revisions );
+
+		/**
+		 * Check the meta values to verify they are NOT revisioned - they are not revisioned by default
+		 */
+
+		// Custom post meta should NOT be restored, orignal value should not be restored, value still 'update1'
+		$this->assertEquals( 'update1', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+		update_post_meta( $post_id, 'meta_revision_test', 'update2' );
+
+
+		/*
+		 * Now test the revisioning of custom meta when enabled by the wp_post_revision_meta_keys filter
+		 */
+
+		// Add the custom field to be revised via the wp_post_revision_meta_keys filter
+		add_filter( 'wp_post_revision_meta_keys', function( $keys ) {
+			$keys[] = 'meta_revision_test';
+			return $keys;
+		});
+
+		// Save the post, changing content to force a revision
+		wp_update_post( array( 'post_content'	=> 'more updated content', 'ID' => $post_id ) );
+
+		$revisions = wp_get_post_revisions( $post_id );
+		$this->assertCount( 5, $revisions );
+
+		// Store custom meta values, which should now be revisioned
+		update_post_meta( $post_id, 'meta_revision_test', 'update3' );
+
+		/**
+		 * Save the post again, custom meta should now be revisioned
+		 *
+		 * Note that a revision is saved even though there is no change
+		 * in post content, becaused the revisioned post_meta has changed
+		 *
+		 */
+		wp_update_post( array( 'ID' => $post_id ) );
+
+		// This revision contains the existing post meta ('update3')
+		$revisions = wp_get_post_revisions( $post_id );
+		$this->assertCount( 6, $revisions );
+
+		// Verify that previous post meta is set
+		$this->assertEquals( 'update3', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+		// Retore the previous revision
+		$revisions = wp_get_post_revisions( $post_id );
+
+		// Go back two to load the previous revision
+		array_shift( $revisions );
+		$last_revision = array_shift( $revisions );
+		wp_restore_post_revision( $last_revision->ID );
+
+		// Verify that previous post meta is restored
+		$this->assertEquals( 'update2', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+		// Try storing a blank meta
+		update_post_meta( $post_id, 'meta_revision_test', '' );
+		wp_update_post( array( 'ID' => $post_id ) );
+
+		update_post_meta( $post_id, 'meta_revision_test', 'update 4' );
+		wp_update_post( array( 'ID' => $post_id ) );
+
+		// Retore the previous revision
+		$revisions = wp_get_post_revisions( $post_id );
+		array_shift( $revisions );
+		$last_revision = array_shift( $revisions );
+		wp_restore_post_revision( $last_revision->ID );
+
+		// Verify that previous post meta is restored
+		$this->assertEquals( '', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+		// Test not tracking a key
+		remove_all_filters( 'wp_post_revision_meta_keys' );
+
+		// Should no longer be revisioned
+		update_post_meta( $post_id, 'meta_revision_test', 'update 5' );
+		wp_update_post( array( 'ID' => $post_id, 'post_content'	=> 'changed content' ) );
+		update_post_meta( $post_id, 'meta_revision_test', 'update 6' );
+		wp_update_post( array( 'ID' => $post_id, 'post_content'	=> 'go updated content' ) );
+		// Retore the previous revision
+		$revisions = wp_get_post_revisions( $post_id );
+		array_shift( $revisions );
+		$last_revision = array_shift( $revisions );
+		wp_restore_post_revision( $last_revision->ID );
+
+		// Verify that previous post meta is NOT restored
+		$this->assertEquals( 'update 6', get_post_meta( $post_id, 'meta_revision_test', true ) );
+
+		// Add the custom field to be revised via the wp_post_revision_meta_keys filter
+		add_filter( 'wp_post_revision_meta_keys', function( $keys ) {
+			$keys[] = 'meta_revision_test';
+			return $keys;
+		});
+
+		/**
+		 * Test the revisioning of multiple meta keys
+		 */
+
+		// Add three values for meta
+		update_post_meta( $post_id, 'meta_revision_test', 'update 7' );
+		add_post_meta( $post_id, 'meta_revision_test', 'update 7 number 2' );
+		add_post_meta( $post_id, 'meta_revision_test', 'update 7 number 3' );
+		wp_update_post( array( 'ID' => $post_id ) );
+
+		// Update all three values
+		update_post_meta( $post_id, 'meta_revision_test', 'update 8', 'update 7' );
+		update_post_meta( $post_id, 'meta_revision_test', 'update 8 number 2', 'update 7 number 2'  );
+		update_post_meta( $post_id, 'meta_revision_test', 'update 8 number 3', 'update 7 number 3'  );
+		wp_update_post( array( 'ID' => $post_id ) );
+
+		// Retore the previous revision
+		$revisions = wp_get_post_revisions( $post_id );
+		array_shift( $revisions );
+		$last_revision = array_shift( $revisions );
+		wp_restore_post_revision( $last_revision->ID );
+
+		$this->assertEquals( array( 'update 7', 'update 7 number 2', 'update 7 number 3' ), get_post_meta( $post_id, 'meta_revision_test' ) );
+
+		// Cleanup!
+		wp_delete_post( $original_post_id );
+
+	}
 }