diff --git a/src/ProxyConnector.php b/src/ProxyConnector.php
index 0bca17e..a3dc166 100644
--- a/src/ProxyConnector.php
+++ b/src/ProxyConnector.php
@@ -256,11 +256,11 @@ public function connect($uri)
 
             // Exception trace arguments are not available on some PHP 7.4 installs
             // @codeCoverageIgnoreStart
-            foreach ($trace as &$one) {
+            foreach ($trace as $ti => $one) {
                 if (isset($one['args'])) {
-                    foreach ($one['args'] as &$arg) {
+                    foreach ($one['args'] as $ai => $arg) {
                         if ($arg instanceof \Closure) {
-                            $arg = 'Object(' . get_class($arg) . ')';
+                            $trace[$ti]['args'][$ai] = 'Object(' . get_class($arg) . ')';
                         }
                     }
                 }
diff --git a/tests/ProxyConnectorTest.php b/tests/ProxyConnectorTest.php
index 6272d6a..59fc466 100644
--- a/tests/ProxyConnectorTest.php
+++ b/tests/ProxyConnectorTest.php
@@ -302,15 +302,17 @@ public function testRejectsWithPreviousIfConnectorRejects()
 
         $promise = $proxy->connect('google.com:80');
 
-        $promise->then(null, $this->expectCallableOnceWithException(
-            'RuntimeException',
-            'Connection to tcp://google.com:80 failed because connection to proxy failed (ECONNREFUSED)',
-            defined('SOCKET_ECONNREFUSED') ? SOCKET_ECONNREFUSED : 111
-        ));
+        $exception = null;
+        $promise->then(null, function ($reason) use (&$exception) {
+            $exception = $reason;
+        });
 
-        $promise->then(null, $this->expectCallableOnceWith($this->callback(function (\Exception $e) use ($previous) {
-            return $e->getPrevious() === $previous;
-        })));
+        assert($exception instanceof \RuntimeException);
+        $this->assertInstanceOf('RuntimeException', $exception);
+        $this->assertEquals('Connection to tcp://google.com:80 failed because connection to proxy failed (ECONNREFUSED)', $exception->getMessage());
+        $this->assertEquals(defined('SOCKET_ECONNREFUSED') ? SOCKET_ECONNREFUSED : 111, $exception->getCode());
+        $this->assertSame($previous, $exception->getPrevious());
+        $this->assertNotEquals('', $exception->getTraceAsString());
     }
 
     public function testRejectsAndClosesIfStreamWritesNonHttp()