diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 3f264505..bfba221a 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -51,14 +51,13 @@ jobs:
             python-version: "3.11"
             gromacs-version: "2022.4"
           # explicitly include a few macOS runners
-          # (conda-forge GROMACS 2023.1 is compiled to use rdtscp CPU instruction but these
-          # are not available in the GitHub runner so we need to use a different GROMACS
-          # version; locally 2023.1 was successfully tested on Intel macOS 13.5. Try 2021.3
-          # from bioconda (2021.1 is on conda-forge, so choosing 2021.3 forces the bioconda
-          # package...)
+          # (conda-forge GROMACS >= 2021 is compiled to use rdtscp CPU instruction but these
+          # are not available in the macOS GitHub runner so we need to use a different GROMACS
+          # version. Try 2021.1 from bioconda, which worked previously.
+          # Locally 2023.1 was successfully tested on Intel macOS 13.5.)
           - os: macOS-latest
             python-version: "3.11"
-            gromacs-version: "2021.3"       
+            gromacs-version: "2021.1"       
             
 
     env: