diff --git a/environment.yml b/environment.yml
index e664b5a9..005e27ec 100644
--- a/environment.yml
+++ b/environment.yml
@@ -24,6 +24,7 @@ dependencies:
   - nbval
   - shyaml
   - pip:
+    - swagger_spec_validator==3.0.3	# CI fails with version 3.0.4
     - black-nb
     # KinFragLib itself
     # - https://github.com/volkamerlab/kinfraglib/archive/master.tar.gz