diff --git a/.github/workflows/pytest.yaml b/.github/workflows/pytest.yaml
index 0d30b3a7d..63e79e4b9 100644
--- a/.github/workflows/pytest.yaml
+++ b/.github/workflows/pytest.yaml
@@ -45,6 +45,9 @@ jobs:
         - { upstream: v3.9.0, python: "3.13" }  # 2024-06-04
         # Development version + latest released Python
         - { upstream: main,   python: "3.13" }
+        # NB Python 3.9 and 3.13 not supported by ixmp4
+        - { upstream: enh/ixmp4, python: "3.10"}
+        - { upstream: enh/ixmp4, python: "3.12"}
 
         exclude:
         # Specific version combinations that are invalid / not to be used
@@ -57,6 +60,7 @@ jobs:
         - { os: macos-latest, version: {upstream: v3.9.0 }}
         # Redundant with macos-latest
         - { os: macos-13, version: {upstream: main }}
+        - { os: macos-13, version: {upstream: enh/ixmp4 }}
 
       fail-fast: false
 
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 283e5f3b9..493c12b6d 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -16,8 +16,8 @@ repos:
     - sdmx1
     - types-PyYAML
     - types-tqdm
-    - "ixmp @ git+https://github.com/iiasa/ixmp.git@main"
-    - "message-ix @ git+https://github.com/iiasa/message_ix.git@main"
+    - "ixmp @ git+https://github.com/iiasa/ixmp.git@enh/ixmp4"
+    - "message-ix @ git+https://github.com/iiasa/message_ix.git@enh/ixmp4"
     args: ["."]
 - repo: https://github.com/astral-sh/ruff-pre-commit
   rev: v0.7.4