diff --git a/scripts/arcanist.php b/scripts/arcanist.php
--- a/scripts/arcanist.php
+++ b/scripts/arcanist.php
@@ -461,11 +461,7 @@
     while ($ex) {
       fwrite(STDERR, $ex->getMessage()."\n");
 
-      if ($ex instanceof PhutilProxyException) {
-        $ex = $ex->getPreviousException();
-      } else {
-        $ex = null;
-      }
+      $ex = $ex->getPrevious();
     }
 
     fwrite(STDERR, phutil_console_format(
diff --git a/src/channel/PhutilJSONProtocolChannel.php b/src/channel/PhutilJSONProtocolChannel.php
--- a/src/channel/PhutilJSONProtocolChannel.php
+++ b/src/channel/PhutilJSONProtocolChannel.php
@@ -101,8 +101,9 @@
           try {
             $objects[] = phutil_json_decode($data);
           } catch (PhutilJSONParserException $ex) {
-            throw new PhutilProxyException(
+            throw new Exception(
               pht('Failed to decode JSON object.'),
+              0,
               $ex);
           }
 
diff --git a/src/conduit/ConduitFuture.php b/src/conduit/ConduitFuture.php
--- a/src/conduit/ConduitFuture.php
+++ b/src/conduit/ConduitFuture.php
@@ -54,10 +54,11 @@
     try {
       $data = phutil_json_decode($raw);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht(
           'Host returned HTTP/200, but invalid JSON data in response to '.
           'a Conduit method call.'),
+        0,
         $ex);
     }
 
diff --git a/src/config/ArcanistConfigurationSourceList.php b/src/config/ArcanistConfigurationSourceList.php
--- a/src/config/ArcanistConfigurationSourceList.php
+++ b/src/config/ArcanistConfigurationSourceList.php
@@ -177,12 +177,13 @@
             $source,
             $raw_value);
         } catch (Exception $ex) {
-          throw new PhutilProxyException(
+          throw new Exception(
             pht(
               'Configuration value ("%s") defined in source "%s" is not '.
               'valid.',
               $key,
               $source->getSourceDisplayName()),
+              0,
             $ex);
         }
       }
diff --git a/src/configuration/ArcanistConfigurationManager.php b/src/configuration/ArcanistConfigurationManager.php
--- a/src/configuration/ArcanistConfigurationManager.php
+++ b/src/configuration/ArcanistConfigurationManager.php
@@ -212,8 +212,9 @@
         try {
           $user_config = phutil_json_decode($user_config_data);
         } catch (PhutilJSONParserException $ex) {
-          throw new PhutilProxyException(
+          throw new Exception(
             pht("Your '%s' file is not a valid JSON file.", '~/.arcrc'),
+            0,
             $ex);
         }
       } else {
@@ -313,10 +314,11 @@
         try {
           $system_config = phutil_json_decode($file);
         } catch (PhutilJSONParserException $ex) {
-          throw new PhutilProxyException(
+          throw new Exception(
             pht(
               "Your '%s' file is not a valid JSON file.",
               $system_config_path),
+            0,
             $ex);
         }
       } else {
diff --git a/src/error/PhutilErrorHandler.php b/src/error/PhutilErrorHandler.php
--- a/src/error/PhutilErrorHandler.php
+++ b/src/error/PhutilErrorHandler.php
@@ -88,18 +88,14 @@
    * can use @{class:PhutilProxyException} to nest exceptions; after PHP 5.3
    * all exceptions are nestable.
    *
+   * @deprecated Call Exception::getPrevious directly.
+   *
    * @param   Exception|Throwable       $ex Exception to unnest.
    * @return  Exception|Throwable|null  Previous exception, if one exists.
    * @task    exutil
    */
   public static function getPreviousException($ex) {
-    if (method_exists($ex, 'getPrevious')) {
-      return $ex->getPrevious();
-    }
-    if (method_exists($ex, 'getPreviousException')) {
-      return $ex->getPreviousException();
-    }
-    return null;
+    return $ex->getPrevious();
   }
 
 
@@ -112,8 +108,8 @@
    */
   public static function getRootException($ex) {
     $root = $ex;
-    while (self::getPreviousException($root)) {
-      $root = self::getPreviousException($root);
+    while ($root->getPrevious()) {
+      $root = $root->getPrevious();
     }
     return $root;
   }
@@ -411,7 +407,7 @@
         $current = $value;
         do {
           $messages[] = '('.get_class($current).') '.$current->getMessage();
-        } while ($current = self::getPreviousException($current));
+        } while ($current = $current->getPrevious());
         $messages = implode(' {>} ', $messages);
 
         if (strlen($messages) > 4096) {
@@ -608,7 +604,7 @@
       }
 
       // If this is a proxy exception, add the proxied exception.
-      $prev = self::getPreviousException($ex);
+      $prev = $ex->getPrevious();
       if ($prev) {
         $stack[] = array(++$id, $prev);
       }
diff --git a/src/error/PhutilProxyException.php b/src/error/PhutilProxyException.php
--- a/src/error/PhutilProxyException.php
+++ b/src/error/PhutilProxyException.php
@@ -6,32 +6,17 @@
  * @{class:PhutilErrorHandler} to unnest exceptions in a forward-compatible way.
  *
  * @concrete-extensible
+ *
+ * @deprecated Use the exception constructor argument $previous directly.
  */
 class PhutilProxyException extends Exception {
 
-  private $previousException;
-
   public function __construct($message, $previous, $code = 0) {
-    $this->previousException = $previous;
-
-    // This may be an "Exception" or a "Throwable". The "__construct()" method
-    // for the Exception is documented as taking an Exception, not a Throwable.
-    // Although passing a Throwable appears to work in PHP 7.3, don't risk it.
-    $is_exception = ($previous instanceof Exception);
-
-    if (version_compare(PHP_VERSION, '5.3.0', '>=') && $is_exception) {
-      parent::__construct($message, $code, $previous);
-    } else {
-      parent::__construct($message, $code);
-    }
+    parent::__construct($message, $code, $previous);
   }
 
   public function getPreviousException() {
-    // NOTE: This can not be named "getPrevious()" because that method is final
-    // after PHP 5.3. Similarly, the property can not be named "previous"
-    // because HPHP declares a property with the same name and "protected"
-    // visibility.
-    return $this->previousException;
+    return $this->getPrevious();
   }
 
 }
diff --git a/src/error/__tests__/PhutilErrorHandlerTestCase.php b/src/error/__tests__/PhutilErrorHandlerTestCase.php
--- a/src/error/__tests__/PhutilErrorHandlerTestCase.php
+++ b/src/error/__tests__/PhutilErrorHandlerTestCase.php
@@ -2,19 +2,6 @@
 
 final class PhutilErrorHandlerTestCase extends PhutilTestCase {
 
-  public function testProxyException() {
-    $a = new Exception('a');
-    $b = new PhutilProxyException('b', $a);
-    $c = new PhutilProxyException('c', $b);
-
-    $this->assertEqual($a, $b->getPrevious());
-    $this->assertEqual($a, PhutilErrorHandler::getRootException($b));
-    $this->assertEqual($a, PhutilErrorHandler::getPreviousException($b));
-
-    $this->assertEqual($a, PhutilErrorHandler::getRootException($c));
-    $this->assertEqual($b, PhutilErrorHandler::getPreviousException($c));
-  }
-
   public function testSilenceHandler() {
     // Errors should normally be logged.
     $this->assertTrue(strlen($this->emitError()) > 0);
diff --git a/src/error/phlog.php b/src/error/phlog.php
--- a/src/error/phlog.php
+++ b/src/error/phlog.php
@@ -26,7 +26,7 @@
       // If this is an exception, proxy it and generate a composite trace which
       // shows both where the phlog() was called and where the exception was
       // originally thrown from.
-      $proxy = new PhutilProxyException('', $event);
+      $proxy = new Exception('', 0, $event);
       $trace = PhutilErrorHandler::getExceptionTrace($proxy);
       $data['trace'] = $trace;
     } else {
diff --git a/src/filesystem/PhutilErrorLog.php b/src/filesystem/PhutilErrorLog.php
--- a/src/filesystem/PhutilErrorLog.php
+++ b/src/filesystem/PhutilErrorLog.php
@@ -44,7 +44,7 @@
           try {
             Filesystem::createDirectory($log_dir, 0755, true);
           } catch (FilesystemException $ex) {
-            throw new PhutilProxyException(
+            throw new Exception(
               pht(
                 'Unable to write log "%s" to path "%s". The containing '.
                 'directory ("%s") does not exist or is not readable, and '.
@@ -52,6 +52,7 @@
                 $this->getLogName(),
                 $log_path,
                 $log_dir),
+              0,
               $ex);
           }
         }
@@ -68,12 +69,13 @@
 
       // If we ran into a write exception and couldn't resolve it, fail.
       if ($write_exception) {
-        throw new PhutilProxyException(
+        throw new Exception(
           pht(
             'Unable to write log "%s" to path "%s" because the path is not '.
             'writable.',
             $this->getLogName(),
             $log_path),
+          0,
           $write_exception);
       }
     }
diff --git a/src/future/asana/PhutilAsanaFuture.php b/src/future/asana/PhutilAsanaFuture.php
--- a/src/future/asana/PhutilAsanaFuture.php
+++ b/src/future/asana/PhutilAsanaFuture.php
@@ -86,8 +86,9 @@
     try {
       $data = phutil_json_decode($body);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht('Expected JSON response from Asana.'),
+        0,
         $ex);
     }
 
diff --git a/src/future/exec/PhutilExecutableFuture.php b/src/future/exec/PhutilExecutableFuture.php
--- a/src/future/exec/PhutilExecutableFuture.php
+++ b/src/future/exec/PhutilExecutableFuture.php
@@ -170,10 +170,11 @@
     try {
       Filesystem::assertExists($cwd);
     } catch (FilesystemException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht(
           'Unable to run a command in directory "%s".',
           $cwd),
+        0,
         $ex);
     }
 
diff --git a/src/future/github/PhutilGitHubFuture.php b/src/future/github/PhutilGitHubFuture.php
--- a/src/future/github/PhutilGitHubFuture.php
+++ b/src/future/github/PhutilGitHubFuture.php
@@ -95,8 +95,9 @@
         $data = array();
       }
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht('Expected JSON response from GitHub.'),
+        0,
         $ex);
     }
 
diff --git a/src/future/http/HTTPSFuture.php b/src/future/http/HTTPSFuture.php
--- a/src/future/http/HTTPSFuture.php
+++ b/src/future/http/HTTPSFuture.php
@@ -439,10 +439,11 @@
                 'Call to "curl_setopt(...)" returned "false".'));
           }
         } catch (Exception $ex) {
-          throw new PhutilProxyException(
+          throw new Exception(
             pht(
               'Call to "curl_setopt(...) failed for option key "%s".',
               $curl_key),
+            0,
             $ex);
         }
       }
diff --git a/src/future/oauth/PhutilOAuth1Future.php b/src/future/oauth/PhutilOAuth1Future.php
--- a/src/future/oauth/PhutilOAuth1Future.php
+++ b/src/future/oauth/PhutilOAuth1Future.php
@@ -303,7 +303,7 @@
     try {
       return phutil_json_decode($body);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(pht('Expected JSON.'), $ex);
+      throw new Exception(pht('Expected JSON.'), 0, $ex);
     }
   }
 
diff --git a/src/future/postmark/PhutilPostmarkFuture.php b/src/future/postmark/PhutilPostmarkFuture.php
--- a/src/future/postmark/PhutilPostmarkFuture.php
+++ b/src/future/postmark/PhutilPostmarkFuture.php
@@ -81,8 +81,9 @@
     try {
       $data = phutil_json_decode($body);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht('Expected JSON response from Postmark.'),
+        0,
         $ex);
     }
 
diff --git a/src/future/slack/PhutilSlackFuture.php b/src/future/slack/PhutilSlackFuture.php
--- a/src/future/slack/PhutilSlackFuture.php
+++ b/src/future/slack/PhutilSlackFuture.php
@@ -71,8 +71,9 @@
     try {
       $data = phutil_json_decode($body);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht('Expected JSON response from Slack.'),
+        0,
         $ex);
     }
 
diff --git a/src/future/twitch/PhutilTwitchFuture.php b/src/future/twitch/PhutilTwitchFuture.php
--- a/src/future/twitch/PhutilTwitchFuture.php
+++ b/src/future/twitch/PhutilTwitchFuture.php
@@ -77,8 +77,9 @@
     try {
       $data = phutil_json_decode($body);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht('Expected JSON response from Twitch.'),
+        0,
         $ex);
     }
 
diff --git a/src/future/wordpress/PhutilWordPressFuture.php b/src/future/wordpress/PhutilWordPressFuture.php
--- a/src/future/wordpress/PhutilWordPressFuture.php
+++ b/src/future/wordpress/PhutilWordPressFuture.php
@@ -72,8 +72,9 @@
     try {
       $data = phutil_json_decode($body);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht('Expected JSON response from WordPress.com.'),
+        0,
         $ex);
     }
 
diff --git a/src/lint/engine/ArcanistConfigurationDrivenLintEngine.php b/src/lint/engine/ArcanistConfigurationDrivenLintEngine.php
--- a/src/lint/engine/ArcanistConfigurationDrivenLintEngine.php
+++ b/src/lint/engine/ArcanistConfigurationDrivenLintEngine.php
@@ -20,12 +20,13 @@
     try {
       $config = phutil_json_decode($data);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht(
           "Expected '%s' file to be a valid JSON file, but ".
           "failed to decode '%s'.",
           '.arclint',
           $config_path),
+        0,
         $ex);
     }
 
@@ -39,8 +40,9 @@
           'linters' => 'map<string, map<string, wild>>',
         ));
     } catch (PhutilTypeCheckException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht("Error in parsing '%s' file.", $config_path),
+        0,
         $ex);
     }
 
@@ -89,11 +91,12 @@
             'exclude' => 'optional regex | list<regex>',
           ) + $more);
       } catch (PhutilTypeCheckException $ex) {
-        throw new PhutilProxyException(
+        throw new Exception(
           pht(
             "Error in parsing '%s' file, for linter '%s'.",
             '.arclint',
             $name),
+          0,
           $ex);
       }
 
@@ -102,12 +105,13 @@
           try {
             $linter->setLinterConfigurationValue($key, $spec[$key]);
           } catch (Exception $ex) {
-            throw new PhutilProxyException(
+            throw new Exception(
               pht(
                 "Error in parsing '%s' file, in key '%s' for linter '%s'.",
                 '.arclint',
                 $key,
                 $name),
+              0,
               $ex);
           }
         }
diff --git a/src/lint/linter/ArcanistJSHintLinter.php b/src/lint/linter/ArcanistJSHintLinter.php
--- a/src/lint/linter/ArcanistJSHintLinter.php
+++ b/src/lint/linter/ArcanistJSHintLinter.php
@@ -119,8 +119,9 @@
       $errors = phutil_json_decode($stdout);
     } catch (PhutilJSONParserException $ex) {
       // Something went wrong and we can't decode the output. Exit abnormally.
-      throw new PhutilProxyException(
+      throw new Exception(
         pht('JSHint returned unparseable output.'),
+        0,
         $ex);
     }
 
diff --git a/src/parser/xhpast/__tests__/PHPASTParserTestCase.php b/src/parser/xhpast/__tests__/PHPASTParserTestCase.php
--- a/src/parser/xhpast/__tests__/PHPASTParserTestCase.php
+++ b/src/parser/xhpast/__tests__/PHPASTParserTestCase.php
@@ -90,10 +90,11 @@
         try {
           $stdout = phutil_json_decode($stdout);
         } catch (PhutilJSONParserException $ex) {
-          throw new PhutilProxyException(
+          throw new Exception(
             pht(
               'Output for test file "%s" is not valid JSON.',
               $name),
+            0,
             $ex);
         }
 
diff --git a/src/parser/xhpast/api/XHPASTTree.php b/src/parser/xhpast/api/XHPASTTree.php
--- a/src/parser/xhpast/api/XHPASTTree.php
+++ b/src/parser/xhpast/api/XHPASTTree.php
@@ -67,8 +67,9 @@
     try {
       $data = phutil_json_decode($stdout);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht('%s: failed to decode tree.', 'XHPAST'),
+        0,
         $ex);
     }
 
diff --git a/src/parser/xhpast/bin/PhutilXHPASTBinary.php b/src/parser/xhpast/bin/PhutilXHPASTBinary.php
--- a/src/parser/xhpast/bin/PhutilXHPASTBinary.php
+++ b/src/parser/xhpast/bin/PhutilXHPASTBinary.php
@@ -81,7 +81,7 @@
         // user to build it themselves.
         self::build();
       } catch (CommandException $ex) {
-        throw new PhutilProxyException(self::getBuildInstructions(), $ex);
+        throw new Exception(self::getBuildInstructions(), 0, $ex);
       }
     }
     $future = new ExecFuture('%s', self::getPath());
diff --git a/src/toolset/ArcanistAlias.php b/src/toolset/ArcanistAlias.php
--- a/src/toolset/ArcanistAlias.php
+++ b/src/toolset/ArcanistAlias.php
@@ -61,10 +61,11 @@
         $alias->toolset = idx($value, 'toolset');
         $alias->command = idx($value, 'command');
       } catch (PhutilTypeCheckException $ex) {
-        $alias->exception = new PhutilProxyException(
+        $alias->exception = new Exception(
           pht(
             'Found invalid alias definition (with key "%s").',
             $key),
+          0,
           $ex);
       }
     } else {
diff --git a/src/unit/engine/ArcanistConfigurationDrivenUnitTestEngine.php b/src/unit/engine/ArcanistConfigurationDrivenUnitTestEngine.php
--- a/src/unit/engine/ArcanistConfigurationDrivenUnitTestEngine.php
+++ b/src/unit/engine/ArcanistConfigurationDrivenUnitTestEngine.php
@@ -33,12 +33,13 @@
     try {
       $config = phutil_json_decode($data);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht(
           "Expected '%s' file to be a valid JSON file, but ".
           "failed to decode '%s'.",
           '.arcunit',
           $config_path),
+        0,
         $ex);
     }
 
@@ -51,8 +52,9 @@
           'engines' => 'map<string, map<string, wild>>',
         ));
     } catch (PhutilTypeCheckException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht("Error in parsing '%s' file.", $config_path),
+        0,
         $ex);
     }
 
@@ -89,11 +91,12 @@
             'exclude' => 'optional regex | list<regex>',
           ));
       } catch (PhutilTypeCheckException $ex) {
-        throw new PhutilProxyException(
+        throw new Exception(
           pht(
             "Error in parsing '%s' file, for test engine '%s'.",
             '.arcunit',
             $name),
+          0,
           $ex);
       }
 
diff --git a/src/utils/utils.php b/src/utils/utils.php
--- a/src/utils/utils.php
+++ b/src/utils/utils.php
@@ -1732,8 +1732,9 @@
   try {
     assert_stringlike($key);
   } catch (InvalidArgumentException $ex) {
-    throw new PhutilProxyException(
+    throw new Exception(
       pht('HTTP query parameter key must be a scalar.'),
+      0,
       $ex);
   }
 
@@ -1742,10 +1743,11 @@
   try {
     assert_stringlike($value);
   } catch (InvalidArgumentException $ex) {
-    throw new PhutilProxyException(
+    throw new Exception(
       pht(
         'HTTP query parameter value (for key "%s") must be a scalar.',
         $key),
+      0,
       $ex);
   }
 
diff --git a/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php b/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php
--- a/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php
+++ b/src/workingcopyidentity/ArcanistWorkingCopyIdentity.php
@@ -206,8 +206,9 @@
     try {
       return phutil_json_decode($raw_config);
     } catch (PhutilJSONParserException $ex) {
-      throw new PhutilProxyException(
+      throw new Exception(
         pht("Unable to parse '%s' file '%s'.", '.arcconfig', $from_where),
+        0,
         $ex);
     }
   }
@@ -306,8 +307,9 @@
           $json = Filesystem::readFile($local_path);
           return phutil_json_decode($json);
         } catch (PhutilJSONParserException $ex) {
-          throw new PhutilProxyException(
+          throw new Exception(
             pht("Failed to parse '%s' as JSON.", $local_path),
+            0,
             $ex);
         }
       } else {