diff --git a/snippets/isDuplexStream.md b/snippets/isDuplexStream.md
index 24e5b05a8..dce0ab19f 100644
--- a/snippets/isDuplexStream.md
+++ b/snippets/isDuplexStream.md
@@ -10,7 +10,6 @@ const isDuplexStream = val =>
   val !== null &&
   typeof val === 'object' &&
   typeof val.pipe === 'function' &&
-  typeof val.pipe === 'function' &&
   typeof val._read === 'function' &&
   typeof val._readableState === 'object' &&
   typeof val._write === 'function' &&