diff --git a/src/parser/xhpast/bin/xhpast_parse.php b/src/parser/xhpast/bin/xhpast_parse.php
index 7c7a901..a8343f4 100644
--- a/src/parser/xhpast/bin/xhpast_parse.php
+++ b/src/parser/xhpast/bin/xhpast_parse.php
@@ -1,63 +1,77 @@
 <?php
 
 /**
  * @group xhpast
  */
 function xhpast_is_available() {
   static $available;
   if ($available === null) {
     $available = false;
     $bin = xhpast_get_binary_path();
     if (Filesystem::pathExists($bin)) {
       list($err, $stdout) = exec_manual('%s --version', $bin);
       if (!$err) {
         $version = trim($stdout);
         if ($version === "xhpast version 5.5.8/1e") {
           $available = true;
         }
       }
     }
   }
   return $available;
 }
 
 
 /**
  * @group xhpast
  */
 function xhpast_get_binary_path() {
   if (phutil_is_windows()) {
     return dirname(__FILE__).'\\xhpast.exe';
   }
   return dirname(__FILE__).'/xhpast';
 }
 
 
 /**
  * @group xhpast
  */
 function xhpast_get_build_instructions() {
   $root = phutil_get_library_root('phutil');
   $make = $root.'/../scripts/build_xhpast.sh';
   $make = Filesystem::resolvePath($make);
   return <<<EOHELP
 Your version of 'xhpast' is unbuilt or out of date. Run this script to build it:
 
   \$ {$make}
 
 EOHELP;
 }
 
 
 /**
  * @group xhpast
  */
 function xhpast_get_parser_future($data) {
   if (!xhpast_is_available()) {
-    throw new Exception(xhpast_get_build_instructions());
+    try {
+      // Try to build XHPAST automatically. If we can't then just ask the user
+      // to build it themselves.
+      xhpast_build();
+    } catch (CommandException $e) {
+      throw new Exception(xhpast_get_build_instructions());
+    }
   }
   $future = new ExecFuture('%s', xhpast_get_binary_path());
   $future->write($data);
 
   return $future;
 }
+
+/**
+ * @group xhpast
+ */
+function xhpast_build() {
+  $root = phutil_get_library_root('phutil');
+  execx('%s', $root.'/../scripts/build_xhpast.sh');
+}