diff --git a/src/error/PhutilOpaqueEnvelopeKey.php b/src/error/PhutilOpaqueEnvelopeKey.php
index 85705b7..9f54def 100644
--- a/src/error/PhutilOpaqueEnvelopeKey.php
+++ b/src/error/PhutilOpaqueEnvelopeKey.php
@@ -1,49 +1,45 @@
 <?php
 
 /**
  * Holds the key for @{class:PhutilOpaqueEnvelope} in a logically distant
  * location so it will never appear in stack traces, etc. You should never need
  * to use this class directly. See @{class:PhutilOpaqueEnvelope} for
  * information about opaque envelopes.
  *
  * @task internal Internals
  */
 final class PhutilOpaqueEnvelopeKey {
 
   private static $key;
 
 
 /* -(  Internals  )---------------------------------------------------------- */
 
 
   /**
    * @task internal
    */
   private function __construct() {
     // <private>
   }
 
 
   /**
    * @task internal
    */
   public static function getKey() {
     if (self::$key === null) {
-      try {
-        self::$key = Filesystem::readRandomBytes(128);
-      } catch (Exception $ex) {
-
-        // NOTE: We can't throw here! Otherwise we might get a stack trace
-        // including the string that was passed to PhutilOpaqueEnvelope's
-        // constructor. Just die() instead.
-
-        die(
-          "Unable to read random bytes in PhutilOpaqueEnvelope. (This ".
-          "causes an immediate process exit to avoid leaking the envelope ".
-          "contents in a stack trace.)");
+      // NOTE: We're using a weak random source because cryptographic levels
+      // of security aren't terribly important here and it allows us to use
+      // envelopes on systems which don't have a strong random source. Notably,
+      // this lets us make it to the readbility check for `/dev/urandom` in
+      // Phabricator on systems where we can't read it.
+      self::$key = '';
+      for ($ii = 0; $ii < 8; $ii++) {
+        self::$key .= md5(mt_rand(), $raw_output = true);
       }
     }
     return self::$key;
   }
 
 }