diff --git a/src/Connection/Internal/Http2ConnectionProcessor.php b/src/Connection/Internal/Http2ConnectionProcessor.php
index f8bf3ae8..6b02b195 100644
--- a/src/Connection/Internal/Http2ConnectionProcessor.php
+++ b/src/Connection/Internal/Http2ConnectionProcessor.php
@@ -409,7 +409,7 @@ public function handleHeaders(int $streamId, array $pseudo, array $headers, bool
             return;
         }
 
-        \assert($stream->preResponseResolution);
+        \assert($stream->preResponseResolution === null);
 
         $stream->preResponseResolution = call(function () use ($stream, $streamId) {
             try {