diff --git a/.github/scripts/set-conda-test-matrix.py b/.github/scripts/set-conda-test-matrix.py
index 69ef0a57e..6bcd0fa6f 100644
--- a/.github/scripts/set-conda-test-matrix.py
+++ b/.github/scripts/set-conda-test-matrix.py
@@ -1,6 +1,8 @@
 """Create test matrix for conda packages in OS/BLAS test matrix workflow."""
 
+import json
 from pathlib import Path
+import re
 
 osmap = {'linux': 'ubuntu',
          'osx': 'macos',
diff --git a/.github/workflows/os-blas-test-matrix.yml b/.github/workflows/os-blas-test-matrix.yml
index 242d89732..263afb7a4 100644
--- a/.github/workflows/os-blas-test-matrix.yml
+++ b/.github/workflows/os-blas-test-matrix.yml
@@ -126,6 +126,7 @@ jobs:
           activate-environment: build-env
           environment-file: .github/conda-env/build-env.yml
           miniforge-version: latest
+          channels: conda-forge,defaults
           channel-priority: strict
           auto-update-conda: false
           auto-activate-base: false
@@ -170,7 +171,10 @@ jobs:
           name: slycot-wheels
           path: slycot-wheels
       - id: set-matrix
-        run: echo "matrix=$(python3 .github/scripts/set-pip-test-matrix.py)" >> $GITHUB_OUTPUT
+        run: |
+          TEMPFILE="$(mktemp)"
+          python3 .github/scripts/set-pip-test-matrix.py | tee $TEMPFILE
+          echo "matrix=$(cat $TEMPFILE)" >> $GITHUB_OUTPUT
 
 
   create-conda-test-matrix:
@@ -194,7 +198,10 @@ jobs:
           name: slycot-conda-pkgs
           path: slycot-conda-pkgs
       - id: set-matrix
-        run: echo "matrix=$(python3 .github/scripts/set-conda-test-matrix.py)" >> $GITHUB_OUTPUT
+        run: |
+          TEMPFILE="$(mktemp)"
+          python3 .github/scripts/set-conda-test-matrix.py | tee $TEMPFILE
+          echo "matrix=$(cat $TEMPFILE)" >> $GITHUB_OUTPUT
 
 
   test-wheel:
@@ -297,6 +304,7 @@ jobs:
           miniforge-version: latest
           activate-environment: test-env
           environment-file: .github/conda-env/test-env.yml
+          channels: conda-forge,defaults
           channel-priority: strict
           auto-activate-base: false
       - name: Download conda packages