diff --git a/contrib/packaging/hgpackaging/pyoxidizer.py b/contrib/packaging/hgpackaging/pyoxidizer.py
--- a/contrib/packaging/hgpackaging/pyoxidizer.py
+++ b/contrib/packaging/hgpackaging/pyoxidizer.py
@@ -12,6 +12,7 @@
 import shutil
 import subprocess
 import sys
+import typing
 
 from .downloads import download_entry
 from .util import (
@@ -69,7 +70,11 @@
 
 
 def run_pyoxidizer(
-    source_dir: pathlib.Path, build_dir: pathlib.Path, target_triple: str,
+    source_dir: pathlib.Path,
+    build_dir: pathlib.Path,
+    target_triple: str,
+    build_vars: typing.Optional[typing.Dict[str, str]] = None,
+    target: typing.Optional[str] = None,
 ) -> pathlib.Path:
     """Run `pyoxidizer` in an environment with access to build dependencies.
 
@@ -77,6 +82,8 @@
     artifacts. Actual build artifacts are likely in a sub-directory with the
     name of the pyoxidizer build target that was built.
     """
+    build_vars = build_vars or {}
+
     # We need to make gettext binaries available for compiling i18n files.
     gettext_pkg, gettext_entry = download_entry('gettext', build_dir)
     gettext_dep_pkg = download_entry('gettext-dep', build_dir)[0]
@@ -104,6 +111,12 @@
         target_triple,
     ]
 
+    for k, v in sorted(build_vars.items()):
+        args.extend(["--var", k, v])
+
+    if target:
+        args.append(target)
+
     subprocess.run(args, env=env, check=True)
 
     return source_dir / "build" / "pyoxidizer" / target_triple / "release"
diff --git a/contrib/packaging/hgpackaging/wix.py b/contrib/packaging/hgpackaging/wix.py
--- a/contrib/packaging/hgpackaging/wix.py
+++ b/contrib/packaging/hgpackaging/wix.py
@@ -22,7 +22,11 @@
     build_py2exe,
     stage_install,
 )
-from .pyoxidizer import create_pyoxidizer_install_layout
+from .pyoxidizer import (
+    build_docs_html,
+    create_pyoxidizer_install_layout,
+    run_pyoxidizer,
+)
 from .util import (
     extract_zip_to_directory,
     normalize_windows_version,
@@ -386,37 +390,65 @@
     """Build a WiX MSI installer using PyOxidizer."""
     hg_build_dir = source_dir / "build"
     build_dir = hg_build_dir / ("wix-%s" % target_triple)
-    staging_dir = build_dir / "stage"
-
-    arch = "x64" if "x86_64" in target_triple else "x86"
 
     build_dir.mkdir(parents=True, exist_ok=True)
-    create_pyoxidizer_install_layout(
-        source_dir, build_dir, staging_dir, target_triple
+
+    # Need to ensure docs HTML is built because this isn't done as part of
+    # `pip install Mercurial`.
+    build_docs_html(source_dir)
+
+    build_vars = {}
+
+    if msi_name:
+        build_vars["MSI_NAME"] = msi_name
+
+    if version:
+        build_vars["VERSION"] = version
+
+    if extra_features:
+        build_vars["EXTRA_MSI_FEATURES"] = ";".join(extra_features)
+
+    if signing_info:
+        if signing_info["cert_path"]:
+            build_vars["SIGNING_PFX_PATH"] = signing_info["cert_path"]
+        if signing_info["cert_password"]:
+            build_vars["SIGNING_PFX_PASSWORD"] = signing_info["cert_password"]
+        if signing_info["subject_name"]:
+            build_vars["SIGNING_SUBJECT_NAME"] = signing_info["subject_name"]
+        if signing_info["timestamp_url"]:
+            build_vars["TIME_STAMP_SERVER_URL"] = signing_info["timestamp_url"]
+
+    if extra_wxs:
+        raise Exception(
+            "support for extra .wxs files has been temporarily dropped"
+        )
+
+    out_dir = run_pyoxidizer(
+        source_dir,
+        build_dir,
+        target_triple,
+        build_vars=build_vars,
+        target="msi",
     )
 
-    # We also install some extra files.
-    process_install_rules(EXTRA_INSTALL_RULES, source_dir, staging_dir)
+    msi_dir = out_dir / "msi"
+    msi_files = [f for f in os.listdir(msi_dir) if f.endswith(".msi")]
 
-    # And remove some files we don't want.
-    for f in STAGING_REMOVE_FILES:
-        p = staging_dir / f
-        if p.exists():
-            print('removing %s' % p)
-            p.unlink()
+    if len(msi_files) != 1:
+        raise Exception("expected exactly 1 .msi file; got %d" % len(msi_files))
+
+    msi_filename = msi_files[0]
 
-    return run_wix_packaging(
-        source_dir,
-        build_dir,
-        staging_dir,
-        arch,
-        version,
-        python2=False,
-        msi_name=msi_name,
-        extra_wxs=extra_wxs,
-        extra_features=extra_features,
-        signing_info=signing_info,
-    )
+    msi_path = msi_dir / msi_filename
+    dist_path = source_dir / "dist" / msi_filename
+
+    dist_path.parent.mkdir(parents=True, exist_ok=True)
+
+    shutil.copyfile(msi_path, dist_path)
+
+    return {
+        "msi_path": dist_path,
+    }
 
 
 def run_wix_packaging(