diff --git a/.github/actions/set-up/action.yaml b/.github/actions/set-up/action.yaml
index 6de2d31e1..126c3ea2f 100644
--- a/.github/actions/set-up/action.yaml
+++ b/.github/actions/set-up/action.yaml
@@ -45,7 +45,7 @@ runs:
     - name: Install Homebrew packages
       # The Protocol Buffer rules need ‘realpath’ from the GNU coreutils.
       shell: bash
-      run: brew update && brew install coreutils
+      run: brew update && brew install coreutils emacs
       if: runner.os == 'macOS'
     - name: Install MSYS2
       uses: msys2/setup-msys2@v2
@@ -57,6 +57,7 @@ runs:
           base-devel
           mingw-w64-x86_64-toolchain
           mingw-w64-x86_64-xpm-nox
+          mingw-w64-x86_64-emacs
       if: runner.os == 'Windows'
     - name: Configure system (Windows)
       # Make Bazel find the right binaries on GitHub.  See
@@ -68,6 +69,7 @@ runs:
       shell: cmd
       run: >-
         ECHO BAZEL_SH=C:\MSYS64\usr\bin\bash.exe>> %GITHUB_ENV%
+        && ECHO EMACS=C:\MSYS64\mingw64\bin\emacs.exe>> %GITHUB_ENV%
         && MKDIR %RUNNER_TEMP%\output-base
         && SUBST O: %RUNNER_TEMP%\output-base
         && ECHO startup --output_base='O:\\'>> github.bazelrc
diff --git a/build.py b/build.py
index 2ffea4171..e526111c2 100755
--- a/build.py
+++ b/build.py
@@ -24,6 +24,7 @@
 import io
 import os
 import pathlib
+import platform
 import shlex
 import shutil
 import subprocess
@@ -91,6 +92,7 @@ def check(self) -> None:
         # Test both default toolchain and versioned toolchains.
         self.test()
         self.versions()
+        self.local()
         self.ext()
 
     @target
@@ -140,6 +142,20 @@ def versions(self) -> None:
             self._test(f'--extra_toolchains=//elisp:emacs_{version}_toolchain',
                        profile=version)
 
+    @target
+    def local(self) -> None:
+        """Runs the Bazel tests under the locally-installed Emacs."""
+        if platform.system() == 'Linux':
+            distribution, release = subprocess.run(
+                ['lsb_release', '--short', '--id', '--release'], check=True,
+                stdout=subprocess.PIPE, encoding='utf-8').stdout.splitlines()
+            if distribution == 'Ubuntu' and release.startswith('22.'):
+                # Once GitHub switches to Ubuntu 24.04, drop this branch.
+                print('Local Emacs is too old')
+                return
+        self._test('--extra_toolchains=//elisp:local_toolchain',
+                   profile='local')
+
     def _test(self, *args: str, profile: str,
               cwd: Optional[pathlib.Path] = None) -> None:
         for bzlmod in (True, False):