diff --git a/conda/environments/cgat-apps.yml b/conda/environments/cgat-apps.yml
index d6e93af1..b64c9aba 100644
--- a/conda/environments/cgat-apps.yml
+++ b/conda/environments/cgat-apps.yml
@@ -23,7 +23,7 @@ dependencies:
 - pep8
 - pybedtools
 - pybigwig
-- pysam>=0.18.0
+- pysam==0.20.0
 - pyyaml
 - quicksect
 - rdflib