diff --git a/lib/compat.php b/lib/compat.php
index 44b2c8d3f94b4a..1c33d2cf38c32c 100644
--- a/lib/compat.php
+++ b/lib/compat.php
@@ -86,6 +86,39 @@ function gutenberg_disable_editor_settings_wpautop( $settings ) {
 }
 add_filter( 'wp_editor_settings', 'gutenberg_disable_editor_settings_wpautop' );
 
+/**
+ * Add TinyMCE fixes for the Classic Editor.
+ *
+ * @see https://core.trac.wordpress.org/ticket/44308
+ */
+function gutenberg_add_classic_editor_fixes() {
+	// Temp add the fix for not creating paragraphs from HTML comments.
+	// TODO: remove after 4.9.7, this should be in core.
+	$script = <<<JS
+jQuery( document ).on( 'tinymce-editor-setup', function( event, editor ) {
+	var hasWpautop = ( window.wp && window.wp.editor && window.wp.editor.autop && editor.getParam( 'wpautop', true ) );
+
+	editor.on( 'BeforeSetContent', function( event ) {
+		if ( event.load && event.format !== 'raw' && ! hasWpautop ) {
+			// Prevent creation of paragraphs out of multiple HTML comments.
+			event.content = event.content.replace( /-->\s+<!--/g, '--><!--' );
+		}
+	});
+
+	editor.on( 'SaveContent', function( event ) {
+		if ( ! hasWpautop ) {
+			// Restore formatting of block boundaries.
+			event.content = event.content.replace( /-->\s*<!-- wp:/g, '-->\\n\\n<!-- wp:' );
+		}
+	});
+});
+JS;
+
+	wp_add_inline_script( 'editor', $script, 'before' );
+
+}
+add_action( 'init', 'gutenberg_add_classic_editor_fixes' );
+
 /**
  * Add rest nonce to the heartbeat response.
  *