diff --git a/requirements.txt b/requirements.txt
index bebcdc1..091f27e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,7 +3,6 @@ requests>=2.16.2
 six >= 1.12.0
 stone>=2,<3.3.3
 # Other dependencies for development
-ply
 pytest
 pytest-runner==5.2.0
 sphinx