diff --git a/.github/requirements-earliest.txt b/.github/requirements-earliest.txt
new file mode 100644
index 0000000..cc72e71
--- /dev/null
+++ b/.github/requirements-earliest.txt
@@ -0,0 +1 @@
+mercurial==5.2
diff --git a/.github/requirements-latest.txt b/.github/requirements-latest.txt
new file mode 100644
index 0000000..3620838
--- /dev/null
+++ b/.github/requirements-latest.txt
@@ -0,0 +1,2 @@
+mercurial
+
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 57efee7..e511200 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,8 +8,70 @@ on:
     branches: [master]
 
 jobs:
-  test:
-    name: Run test suite
+  test-earliest:
+    name: Run test suite on the earliest supported Python version
+    runs-on: ubuntu-20.04
+
+    steps:
+      - uses: actions/checkout@v4
+        name: Checkout repository
+        with:
+          fetch-depth: 1
+          submodules: 'recursive'
+      - uses: actions/setup-python@v5
+        id: earliest
+        with:
+          python-version: '3.7.x'
+          check-latest: true
+          cache: 'pip'
+          cache-dependency-path: '**/requirements-earliest.txt'
+
+      - name: Install dependencies
+        run: |
+            python -m pip install --upgrade pip
+            pip install -r .github/requirements-earliest.txt
+
+      - name: Report selected versions
+        run: |
+          echo Selected '${{ steps.earliest.outputs.python-version }}'
+          ./hg-fast-export.sh --debug
+
+      - name: Run tests on earliest supported Python version
+        run: make -C t
+
+  test-latest:
+    name: Run test suite on the latest supported python version
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+        name: Checkout repository
+        with:
+          fetch-depth: 1
+          submodules: 'recursive'
+      - uses: actions/setup-python@v5
+        id: latest
+        with:
+          python-version: '3.x'
+          check-latest: true
+          cache: 'pip'
+          cache-dependency-path: '**/requirements-latest.txt'
+
+      - name: Install dependencies
+        run: |
+            python -m pip install --upgrade pip
+            pip install -r .github/requirements-latest.txt
+
+      - name: Report selected version
+        run: |
+          echo Selected '${{ steps.latest.outputs.python-version }}'
+          ./hg-fast-export.sh --debug
+
+      - name: Run tests on 3.x
+        run: make -C t
+
+  code-quality:
+    name: Run code quality checks
     runs-on: ubuntu-latest
 
     steps:
@@ -19,9 +81,6 @@ jobs:
         fetch-depth: 1
         submodules: 'recursive'
 
-    - name: Run tests
-      run: make -C t
-
     - name: Initialize CodeQL
       uses: github/codeql-action/init@v2
       with:
diff --git a/README.md b/README.md
index b4aa33c..abd9a70 100644
--- a/README.md
+++ b/README.md
@@ -29,9 +29,9 @@ first time.
 System Requirements
 -------------------
 
-This project depends on Python 3.5+, and the Mercurial >= 5.2 package.
-If Python is not installed, install it before proceeding. The Mercurial
-package can be installed with `pip install mercurial`.
+This project depends on Python (>=3.7) and the Mercurial package (>=
+5.2).  If Python is not installed, install it before proceeding. The
+Mercurial package can be installed with `pip install mercurial`.
 
 On windows the bash that comes with "Git for Windows" is known to work
 well.
diff --git a/hg-fast-export.sh b/hg-fast-export.sh
index be52c5d..7d6d7b7 100755
--- a/hg-fast-export.sh
+++ b/hg-fast-export.sh
@@ -45,6 +45,14 @@ if [ -z "${PYTHON}" ]; then
     exit 1
 fi
 
+"${PYTHON}" -c 'import sys; exit(sys.version_info.major==3 and sys.version_info.minor >= 7)'
+
+if [ $? -eq 0 ]; then
+    echo "Could not find an interpreter for a supported Python version (>= 3.7)" \
+        "Please use the 'PYTHON' environment variable to specify the interpreter to use."
+    exit 1
+fi
+
 USAGE="[--quiet] [-r <repo>] [--force] [--ignore-unnamed-heads] [-m <max>] [-s] [--hgtags] [-A <file>] [-B <file>] [-T <file>] [-M <name>] [-o <name>] [--hg-hash] [-e <encoding>]"
 LONG_USAGE="Import hg repository <repo> up to either tip or <max>
 If <repo> is omitted, use last hg repository as obtained from state file,
@@ -86,6 +94,14 @@ case "$1" in
       echo ""
       echo "$LONG_USAGE"
       exit 0
+      ;;
+
+    --debug)
+      echo -n "Using Python: "
+      "${PYTHON}" --version
+      echo -n "Using Mercurial: "
+      hg --version
+      exit 0
 esac
 
 IS_BARE=$(git rev-parse --is-bare-repository) \