diff --git a/setup.py b/setup.py
index 880face..a3d0176 100755
--- a/setup.py
+++ b/setup.py
@@ -43,7 +43,7 @@
         exclude=["*.tests", "*.tests.*", "tests.*", "tests"]),
     install_requires=[
         'cheetah3>=3.0.0,<4.0',
-        'pyyaml>=5.0,!=5.4.0,!=5.4.1,<6.0',
+        'pyyaml>=5.0,!=5.4.0,!=5.4.1,!=6.0,<7.0',
         'requests>=2.0.0,<3.0.0',
         'blessings<2.0',
         'ruamel.yaml<0.16.0;python_version < "3.7"',