diff --git a/src/__phutil_library_init__.php b/src/__phutil_library_init__.php
--- a/src/__phutil_library_init__.php
+++ b/src/__phutil_library_init__.php
@@ -17,7 +17,6 @@
   try {
     $loader = new PhutilSymbolLoader();
     $symbols = $loader
-      ->setType('class')
       ->setName($class_name)
       ->selectAndLoadSymbols();
 
diff --git a/src/__phutil_library_map__.php b/src/__phutil_library_map__.php
--- a/src/__phutil_library_map__.php
+++ b/src/__phutil_library_map__.php
@@ -253,7 +253,6 @@
     'PhutilParserGeneratorException' => 'parser/generator/exception/PhutilParserGeneratorException.php',
     'PhutilParserGeneratorTestCase' => 'parser/__tests__/PhutilParserGeneratorTestCase.php',
     'PhutilPayPalAPIFuture' => 'future/paypal/PhutilPayPalAPIFuture.php',
-    'PhutilPerson' => 'internationalization/PhutilPerson.php',
     'PhutilPersonTest' => 'internationalization/__tests__/PhutilPersonTest.php',
     'PhutilPersonaAuthAdapter' => 'auth/PhutilPersonaAuthAdapter.php',
     'PhutilPhabricatorAuthAdapter' => 'auth/PhutilPhabricatorAuthAdapter.php',
@@ -264,7 +263,6 @@
     'PhutilProxyException' => 'error/PhutilProxyException.php',
     'PhutilPygmentsSyntaxHighlighter' => 'markup/syntax/highlighter/PhutilPygmentsSyntaxHighlighter.php',
     'PhutilPythonFragmentLexer' => 'lexer/PhutilPythonFragmentLexer.php',
-    'PhutilQsprintfInterface' => 'xsprintf/PhutilQsprintfInterface.php',
     'PhutilQueryStringParser' => 'parser/PhutilQueryStringParser.php',
     'PhutilQueryStringParserTestCase' => 'parser/__tests__/PhutilQueryStringParserTestCase.php',
     'PhutilRainbowSyntaxHighlighter' => 'markup/syntax/highlighter/PhutilRainbowSyntaxHighlighter.php',
@@ -304,7 +302,6 @@
     'PhutilRope' => 'utils/PhutilRope.php',
     'PhutilRopeTestCase' => 'utils/__tests__/PhutilRopeTestCase.php',
     'PhutilSafeHTML' => 'markup/PhutilSafeHTML.php',
-    'PhutilSafeHTMLProducerInterface' => 'markup/PhutilSafeHTMLProducerInterface.php',
     'PhutilSafeHTMLTestCase' => 'markup/__tests__/PhutilSafeHTMLTestCase.php',
     'PhutilSaturateStdoutDaemon' => 'daemon/torture/PhutilSaturateStdoutDaemon.php',
     'PhutilServiceProfiler' => 'serviceprofiler/PhutilServiceProfiler.php',
@@ -486,6 +483,11 @@
     'xsprintf_terminal' => 'xsprintf/tsprintf.php',
     'xsprintf_uri' => 'xsprintf/urisprintf.php',
   ),
+  'interface' => array(
+    'PhutilPerson' => 'internationalization/PhutilPerson.php',
+    'PhutilQsprintfInterface' => 'xsprintf/PhutilQsprintfInterface.php',
+    'PhutilSafeHTMLProducerInterface' => 'markup/PhutilSafeHTMLProducerInterface.php',
+  ),
   'xmap' => array(
     'AASTNode' => 'Phobject',
     'AASTNodeList' => array(
diff --git a/src/moduleutils/PhutilLibraryMapBuilder.php b/src/moduleutils/PhutilLibraryMapBuilder.php
--- a/src/moduleutils/PhutilLibraryMapBuilder.php
+++ b/src/moduleutils/PhutilLibraryMapBuilder.php
@@ -278,12 +278,15 @@
    * Build a map of all source files in a library to hashes of their content.
    * Returns an array like this:
    *
-   *   array(
-   *     'src/parser/ExampleParser.php' => '60b725f10c9c85c70d97880dfe8191b3',
-   *     // ...
-   *   );
+   * ```lang=php
+   * array(
+   *   'src/parser/ExampleParser.php' => '60b725f10c9c85c70d97880dfe8191b3',
+   *   // ...
+   * );
+   * ```
    *
    * @return dict  Map of library-relative paths to content hashes.
+   *
    * @task source
    */
   private function loadSourceFileMap() {
@@ -335,11 +338,13 @@
    *
    * @param   dict  Symbol analysis of all source files.
    * @return  dict  Library map.
+   *
    * @task source
    */
   private function buildLibraryMap(array $symbol_map) {
     $library_map = array(
       'class'     => array(),
+      'interface' => array(),
       'function'  => array(),
       'xmap'      => array(),
     );
@@ -348,9 +353,8 @@
     foreach ($symbol_map as $file => $info) {
       foreach ($info['have'] as $type => $symbols) {
         foreach ($symbols as $symbol => $declaration) {
-          $lib_type = ($type == 'interface') ? 'class' : $type;
-          if (!empty($library_map[$lib_type][$symbol])) {
-            $prior = $library_map[$lib_type][$symbol];
+          if (!empty($library_map[$type][$symbol])) {
+            $prior = $library_map[$type][$symbol];
             throw new Exception(
               pht(
                 "Definition of %s '%s' in file '%s' duplicates prior ".
@@ -361,7 +365,7 @@
                 $file,
                 $prior));
           }
-          $library_map[$lib_type][$symbol] = $file;
+          $library_map[$type][$symbol] = $file;
         }
       }
       $library_map['xmap'] += $info['xmap'];
@@ -388,7 +392,7 @@
   /**
    * Write a finalized library map.
    *
-   * @param  dict Library map structure to write.
+   * @param  dict  Library map structure to write.
    * @return void
    *
    * @task source
diff --git a/src/symbols/PhutilSymbolLoader.php b/src/symbols/PhutilSymbolLoader.php
--- a/src/symbols/PhutilSymbolLoader.php
+++ b/src/symbols/PhutilSymbolLoader.php
@@ -174,11 +174,12 @@
     }
 
     if ($this->type) {
-      $types = array($this->type);
+      $types = (array)$this->type;
     } else {
       $types = array(
         'class',
         'function',
+        'interface',
       );
     }
 
@@ -193,12 +194,6 @@
     foreach ($libraries as $library) {
       $map = $bootloader->getLibraryMap($library);
       foreach ($types as $type) {
-        if ($type == 'interface') {
-          $lookup_map = $map['class'];
-        } else {
-          $lookup_map = $map[$type];
-        }
-
         // As an optimization, we filter the list of candidate symbols in
         // several passes, applying a name-based filter first if possible since
         // it is highly selective and guaranteed to match at most one symbol.
@@ -210,9 +205,9 @@
         if ($this->name) {
           // If we have a name filter, just pick the matching name out if it
           // exists.
-          if (isset($lookup_map[$this->name])) {
+          if (isset($map[$type][$this->name])) {
             $filtered_map = array(
-              $this->name => $lookup_map[$this->name],
+              $this->name => $map[$type][$this->name],
             );
           } else {
             $filtered_map = array();
@@ -220,13 +215,13 @@
         } else if ($names !== null) {
           $filtered_map = array();
           foreach ($names as $name => $ignored) {
-            if (isset($lookup_map[$name])) {
-              $filtered_map[$name] = $lookup_map[$name];
+            if (isset($map[$type][$name])) {
+              $filtered_map[$name] = $map[$type][$name];
             }
           }
         } else {
           // Otherwise, start with everything.
-          $filtered_map = $lookup_map;
+          $filtered_map = $map[$type];
         }
 
         if ($this->pathPrefix) {
@@ -320,7 +315,7 @@
   public function loadObjects(array $argv = array()) {
     $symbols = $this
       ->setConcreteOnly(true)
-      ->setType('class')
+      ->setType(array('class', 'interface'))
       ->selectAndLoadSymbols();
 
     $objects = array();