diff --git a/devtools/conda-envs/test_env.yaml b/devtools/conda-envs/test_env.yaml
index a78abaab..df4a45f9 100644
--- a/devtools/conda-envs/test_env.yaml
+++ b/devtools/conda-envs/test_env.yaml
@@ -15,7 +15,7 @@ dependencies:
   - openmm >=7.3
   - mdtraj >=1.7.2
   - openmmtools >=0.18.3
-  - pymbar
+  - pymbar <4
   - ambermini >=16.16.0
   - docopt
   - openmoltools >=0.7.5
@@ -39,4 +39,4 @@ dependencies:
   - jinja2
   - runipy
   - pip:
-      - msmb_theme
\ No newline at end of file
+      - msmb_theme