diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 7b47a63..2da86ba 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -31,12 +31,14 @@ jobs:
         auto-update-conda: true
         python-version: ${{ matrix.python-version }}
         environment-file: continuous_integration/environment.yml
-        channels: conda-forge
+        channels: conda-forge,nodefaults
+        channel-priority: strict
         activate-environment: suitesparse-graphblas
+        auto-activate-base: false
     - name: GraphBLAS (from conda-forge)
       if: (contains(matrix.source, 'conda-forge'))
       run: |
-        conda install -c conda-forge graphblas=${{ matrix.graphblas-version }} pytest-randomly
+        conda install graphblas=${{ matrix.graphblas-version }}
     - name: GraphBLAS (from source)
       if: (contains(matrix.source, 'source'))
       run: |
diff --git a/continuous_integration/environment.yml b/continuous_integration/environment.yml
index 22064d0..a5c0d41 100644
--- a/continuous_integration/environment.yml
+++ b/continuous_integration/environment.yml
@@ -1,13 +1,12 @@
 name: suitesparse-graphblas
 channels:
   - conda-forge
-  - defaults
+  - nodefaults  # Only install packages from conda-forge for faster solving
 dependencies:
   # - graphblas=6.0.2
   - cffi
   - cython
   - numpy
   - pytest
+  - pytest-randomly
   - coverage
-  - black
-  - flake8
diff --git a/suitesparse.sh b/suitesparse.sh
index 891391e..56c6784 100755
--- a/suitesparse.sh
+++ b/suitesparse.sh
@@ -1,10 +1,12 @@
 #!/bin/bash
 
+set -x  # echo on
+
 # parse SuiteSparse version from first argument, a git tag that ends in the version (no leading v)
 if [[ $1 =~ refs/tags/([0-9]*\.[0-9]*\.[0-9]*)\..*$ ]]; then
     VERSION=${BASH_REMATCH[1]}
 else
-    echo "Specify a SuiteSparse version, such as: $0 refs/tags/7.4.3.0"
+    echo "Specify a SuiteSparse version, such as: $0 refs/tags/7.4.3.0 (got: $1)"
     exit -1
 fi
 echo VERSION: $VERSION