diff --git a/src/manage/scriptutils.py b/src/manage/scriptutils.py
index 784ab01..d203d8c 100644
--- a/src/manage/scriptutils.py
+++ b/src/manage/scriptutils.py
@@ -48,8 +48,16 @@ def _find_shebang_command(cmd, full_cmd, *, windowed=None):
     if not sh_cmd.match("*.exe"):
         sh_cmd = sh_cmd.with_name(sh_cmd.name + ".exe")
 
-    is_wdefault = sh_cmd.match("pythonw.exe") or sh_cmd.match("pyw.exe")
-    is_default = is_wdefault or sh_cmd.match("python.exe") or sh_cmd.match("py.exe")
+    is_wdefault = (
+        sh_cmd.match("pythonw.exe")
+        or sh_cmd.match("pyw.exe")
+        or sh_cmd.match("pythonw3.exe")
+    )
+    is_default = is_wdefault or (
+        sh_cmd.match("python.exe")
+        or sh_cmd.match("py.exe")
+        or sh_cmd.match("python3.exe")
+    )
 
     # Internal logic error, but non-fatal, if it has no value
     assert windowed is not None
diff --git a/tests/conftest.py b/tests/conftest.py
index c4ec097..a08d35f 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -178,8 +178,15 @@ def get_install_to_run(self, tag, *, windowed=False):
             return i
 
         company, _, tag = tag.replace("/", "\\").rpartition("\\")
-        return [i for i in self.installs
-                if (not tag or i["tag"] == tag) and (not company or i["company"] == company)][0]
+        try:
+            found = [i for i in self.installs
+                     if (not tag or i["tag"] == tag) and (not company or i["company"] == company)]
+        except LookupError as ex:
+            # LookupError is expected from this function, so make sure we don't raise it here
+            raise RuntimeError from ex
+        if found:
+            return found[0]
+        raise LookupError(tag)
 
     def ask_yn(self, question):
         return False if self.confirm else True
diff --git a/tests/test_scriptutils.py b/tests/test_scriptutils.py
index f81d575..9ccf506 100644
--- a/tests/test_scriptutils.py
+++ b/tests/test_scriptutils.py
@@ -139,8 +139,8 @@ def test_read_shebang_windowed(fake_config, tmp_path, script, expect, windowed):
 def test_default_py_shebang(fake_config, tmp_path):
     inst = _fake_install("1.0", company="PythonCore", prefix=PurePath("C:\\TestRoot"), default=True)
     inst["run-for"] = [
-        dict(name="python.exe", target=".\\python.exe"),
-        dict(name="pythonw.exe", target=".\\pythonw.exe", windowed=1),
+        dict(name="othername.exe", target=".\\test-binary-1.0.exe"),
+        dict(name="othernamew.exe", target=".\\test-binary-1.0-w.exe", windowed=1),
     ]
     fake_config.installs[:] = [inst]
 
@@ -150,11 +150,13 @@ def t(n):
     # Finds the install's default executable
     assert t("python")["executable"].match("test-binary-1.0.exe")
     assert t("py")["executable"].match("test-binary-1.0.exe")
+    assert t("python3")["executable"].match("test-binary-1.0.exe")
     assert t("python1.0")["executable"].match("test-binary-1.0.exe")
     # Finds the install's run-for executable with windowed=1
-    assert t("pythonw")["executable"].match("pythonw.exe")
-    assert t("pyw")["executable"].match("pythonw.exe")
-    assert t("pythonw1.0")["executable"].match("pythonw.exe")
+    assert t("pythonw")["executable"].match("test-binary-1.0-w.exe")
+    assert t("pyw")["executable"].match("test-binary-1.0-w.exe")
+    assert t("pythonw3")["executable"].match("test-binary-1.0-w.exe")
+    assert t("pythonw1.0")["executable"].match("test-binary-1.0-w.exe")
 
 
 def test_unmanaged_py_shebang(fake_config, tmp_path):