diff --git a/conf/default.conf.php b/conf/default.conf.php
index 897b0f5734..e811b54f76 100644
--- a/conf/default.conf.php
+++ b/conf/default.conf.php
@@ -334,6 +334,13 @@ return array(
 
   'differential.revision-custom-detail-renderer'  => null,
 
+  // Array for custom remarkup rules. The array should have a list of
+  // class names of classes that extend PhutilRemarkupRule
+  'differential.custom-remarkup-rules' => null,
+
+  // Array for custom remarkup block rules. The array should have a list of
+  // class names of classes that extend PhutilRemarkupEngineBlockRule
+  'differential.custom-remarkup-block-rules' => null,
 
 // -- Maniphest ------------------------------------------------------------- //
 
diff --git a/src/applications/differential/parser/markup/DifferentialMarkupEngineFactory.php b/src/applications/differential/parser/markup/DifferentialMarkupEngineFactory.php
index 00c4e38849..abf48c5c0c 100644
--- a/src/applications/differential/parser/markup/DifferentialMarkupEngineFactory.php
+++ b/src/applications/differential/parser/markup/DifferentialMarkupEngineFactory.php
@@ -48,6 +48,15 @@ class DifferentialMarkupEngineFactory {
     $rules[] = new PhutilRemarkupRuleBold();
     $rules[] = new PhutilRemarkupRuleItalic();
 
+    $custom_rule_classes =
+      PhabricatorEnv::getEnvConfig('differential.custom-remarkup-rules');
+    if ($custom_rule_classes) {
+      foreach ($custom_rule_classes as $custom_rule_class) {
+        PhutilSymbolLoader::loadClass($custom_rule_class);
+        $rules[] = newv($custom_rule_class, array());
+      }
+    }
+
     $blocks = array();
     $blocks[] = new PhutilRemarkupEngineRemarkupQuotesBlockRule();
     $blocks[] = new PhutilRemarkupEngineRemarkupHeaderBlockRule();
@@ -55,6 +64,15 @@ class DifferentialMarkupEngineFactory {
     $blocks[] = new PhutilRemarkupEngineRemarkupCodeBlockRule();
     $blocks[] = new PhutilRemarkupEngineRemarkupDefaultBlockRule();
 
+    $custom_block_rule_classes =
+      PhabricatorEnv::getEnvConfig('differential.custom-remarkup-block-rules');
+    if ($custom_block_rule_classes) {
+      foreach ($custom_block_rule_classes as $custom_block_rule_class) {
+        PhutilSymbolLoader::loadClass($custom_block_rule_class);
+        $blocks[] = newv($custom_block_rule_class, array());
+      }
+    }
+
     foreach ($blocks as $block) {
       if (!($block instanceof PhutilRemarkupEngineRemarkupCodeBlockRule)) {
         $block->setMarkupRules($rules);
diff --git a/src/applications/differential/parser/markup/__init__.php b/src/applications/differential/parser/markup/__init__.php
index bcd31d17e2..16e58bca7b 100644
--- a/src/applications/differential/parser/markup/__init__.php
+++ b/src/applications/differential/parser/markup/__init__.php
@@ -26,6 +26,8 @@ phutil_require_module('phutil', 'markup/engine/remarkup/markuprule/escaperemarku
 phutil_require_module('phutil', 'markup/engine/remarkup/markuprule/hyperlink');
 phutil_require_module('phutil', 'markup/engine/remarkup/markuprule/italics');
 phutil_require_module('phutil', 'markup/engine/remarkup/markuprule/monospace');
+phutil_require_module('phutil', 'symbols');
+phutil_require_module('phutil', 'utils');
 
 
 phutil_require_source('DifferentialMarkupEngineFactory.php');