diff --git a/src/poetry/console/commands/install.py b/src/poetry/console/commands/install.py
index 9895745b48b..ad5b574ab37 100644
--- a/src/poetry/console/commands/install.py
+++ b/src/poetry/console/commands/install.py
@@ -93,6 +93,19 @@ def activated_groups(self) -> set[str]:
     def _alternative_sync_command(self) -> str:
         return "poetry sync"
 
+    @property
+    def _with_synchronization(self) -> bool:
+        with_synchronization = self.option("sync")
+        if with_synchronization:
+            self.line_error(
+                "<warning>The `<fg=yellow;options=bold>--sync</>` option is"
+                " deprecated and slated for removal in the next minor release"
+                " after June 2025, use the"
+                f" `<fg=yellow;options=bold>{self._alternative_sync_command}</>`"
+                " command instead.</warning>"
+            )
+        return bool(with_synchronization)
+
     def handle(self) -> int:
         from poetry.core.masonry.utils.module import ModuleOrPackageNotFoundError
 
@@ -150,20 +163,10 @@ def handle(self) -> int:
 
         self.installer.extras(extras)
 
-        with_synchronization = self.option("sync")
-        if with_synchronization:
-            self.line_error(
-                "<warning>The `<fg=yellow;options=bold>--sync</>` option is"
-                " deprecated and slated for removal in the next minor release"
-                " after June 2025, use the"
-                f" `<fg=yellow;options=bold>{self._alternative_sync_command}</>`"
-                " command instead.</warning>"
-            )
-
         self.installer.only_groups(self.activated_groups)
         self.installer.skip_directory(self.option("no-directory"))
         self.installer.dry_run(self.option("dry-run"))
-        self.installer.requires_synchronization(with_synchronization)
+        self.installer.requires_synchronization(self._with_synchronization)
         self.installer.executor.enable_bytecode_compilation(self.option("compile"))
         self.installer.verbose(self.io.is_verbose())
 
diff --git a/src/poetry/console/commands/self/sync.py b/src/poetry/console/commands/self/sync.py
index 0af576c7b80..05fc0c25a3b 100644
--- a/src/poetry/console/commands/self/sync.py
+++ b/src/poetry/console/commands/self/sync.py
@@ -29,3 +29,7 @@ class SelfSyncCommand(SelfInstallCommand):
 You can add more packages using the <c1>self add</c1> command and remove them using \
 the <c1>self remove</c1> command.
 """
+
+    @property
+    def _with_synchronization(self) -> bool:
+        return True
diff --git a/src/poetry/console/commands/sync.py b/src/poetry/console/commands/sync.py
index 29d6c1be873..4723483f725 100644
--- a/src/poetry/console/commands/sync.py
+++ b/src/poetry/console/commands/sync.py
@@ -34,3 +34,7 @@ class SyncCommand(InstallCommand):
 If you want to use Poetry only for dependency management but not for packaging,
 you can set the "package-mode" to false in your pyproject.toml file.
 """
+
+    @property
+    def _with_synchronization(self) -> bool:
+        return True
diff --git a/src/poetry/utils/env/__init__.py b/src/poetry/utils/env/__init__.py
index c3834f4fbaf..9ab3b37d021 100644
--- a/src/poetry/utils/env/__init__.py
+++ b/src/poetry/utils/env/__init__.py
@@ -21,7 +21,6 @@
 from poetry.utils.env.script_strings import GET_ENV_PATH_ONELINER
 from poetry.utils.env.script_strings import GET_ENVIRONMENT_INFO
 from poetry.utils.env.script_strings import GET_PATHS
-from poetry.utils.env.script_strings import GET_PATHS_FOR_GENERIC_ENVS
 from poetry.utils.env.script_strings import GET_PYTHON_VERSION_ONELINER
 from poetry.utils.env.script_strings import GET_SYS_PATH
 from poetry.utils.env.site_packages import SitePackages
@@ -97,7 +96,6 @@ def build_environment(
     "GET_SYS_PATH",
     "GET_ENV_PATH_ONELINER",
     "GET_PYTHON_VERSION_ONELINER",
-    "GET_PATHS_FOR_GENERIC_ENVS",
     "EnvError",
     "EnvCommandError",
     "IncorrectEnvError",
diff --git a/src/poetry/utils/env/base_env.py b/src/poetry/utils/env/base_env.py
index f57fb9cc2ae..3c0da4ffa20 100644
--- a/src/poetry/utils/env/base_env.py
+++ b/src/poetry/utils/env/base_env.py
@@ -175,13 +175,10 @@ def os(self) -> str:
     @property
     def site_packages(self) -> SitePackages:
         if self._site_packages is None:
-            # we disable write checks if no user site exist
-            fallbacks = [self.usersite] if self.usersite else []
             self._site_packages = SitePackages(
                 self.purelib,
                 self.platlib,
-                fallbacks,
-                skip_write_checks=not fallbacks,
+                self.fallbacks,
             )
         return self._site_packages
 
@@ -214,8 +211,14 @@ def platlib(self) -> Path:
 
         return self._platlib
 
+    @cached_property
+    def fallbacks(self) -> list[Path]:
+        paths = [Path(path) for path in self.paths.get("fallbacks", [])]
+        paths += [self.usersite] if self.usersite else []
+        return paths
+
     def _get_lib_dirs(self) -> list[Path]:
-        return [self.purelib, self.platlib]
+        return [self.purelib, self.platlib, *self.fallbacks]
 
     def is_path_relative_to_lib(self, path: Path) -> bool:
         for lib_path in self._get_lib_dirs():
diff --git a/src/poetry/utils/env/generic_env.py b/src/poetry/utils/env/generic_env.py
index 276d1b1eb18..28ab156d5a1 100644
--- a/src/poetry/utils/env/generic_env.py
+++ b/src/poetry/utils/env/generic_env.py
@@ -8,7 +8,7 @@
 from typing import TYPE_CHECKING
 from typing import Any
 
-from poetry.utils.env.script_strings import GET_PATHS_FOR_GENERIC_ENVS
+from poetry.utils.env.script_strings import GET_PATHS
 from poetry.utils.env.virtual_env import VirtualEnv
 
 
@@ -78,7 +78,7 @@ def find_executables(self) -> None:
                 self._pip_executable = pip_executable
 
     def get_paths(self) -> dict[str, str]:
-        output = self.run_python_script(GET_PATHS_FOR_GENERIC_ENVS)
+        output = self.run_python_script(GET_PATHS)
 
         paths: dict[str, str] = json.loads(output)
         return paths
diff --git a/src/poetry/utils/env/script_strings.py b/src/poetry/utils/env/script_strings.py
index dc33e00ba05..a2935b566e9 100644
--- a/src/poetry/utils/env/script_strings.py
+++ b/src/poetry/utils/env/script_strings.py
@@ -92,18 +92,16 @@ def _version_nodot(version):
 
 GET_PATHS = """\
 import json
-import sysconfig
-
-print(json.dumps(sysconfig.get_paths()))
-"""
-
-GET_PATHS_FOR_GENERIC_ENVS = """\
-import json
 import site
 import sysconfig
 
 paths = sysconfig.get_paths().copy()
 
+paths["fallbacks"] = [
+    p for p in site.getsitepackages()
+    if p and p not in {paths.get("purelib"), paths.get("platlib")}
+]
+
 if site.check_enableusersite():
     paths["usersite"] = site.getusersitepackages()
     paths["userbase"] = site.getuserbase()
diff --git a/src/poetry/utils/env/site_packages.py b/src/poetry/utils/env/site_packages.py
index a082419031c..564aa003aa0 100644
--- a/src/poetry/utils/env/site_packages.py
+++ b/src/poetry/utils/env/site_packages.py
@@ -25,7 +25,6 @@ def __init__(
         purelib: Path,
         platlib: Path | None = None,
         fallbacks: list[Path] | None = None,
-        skip_write_checks: bool = False,
     ) -> None:
         self._purelib = purelib
         self._platlib = platlib or purelib
@@ -40,7 +39,7 @@ def __init__(
             if path not in self._candidates:
                 self._candidates.append(path)
 
-        self._writable_candidates = None if not skip_write_checks else self._candidates
+        self._writable_candidates: list[Path] | None = None
 
     @property
     def path(self) -> Path:
diff --git a/tests/console/commands/self/test_install.py b/tests/console/commands/self/test_install.py
index a5e15e41ed6..0cd9663a4f9 100644
--- a/tests/console/commands/self/test_install.py
+++ b/tests/console/commands/self/test_install.py
@@ -56,14 +56,9 @@ def test_self_install(
 
     tester.execute()
 
-    expected_output = """\
-Updating dependencies
-Resolving dependencies...
-
-Writing lock file
-"""
-
-    assert tester.io.fetch_output() == expected_output
+    output = tester.io.fetch_output()
+    assert output.startswith("Updating dependencies")
+    assert output.endswith("Writing lock file\n")
     assert tester.io.fetch_error() == ""
 
 
diff --git a/tests/console/commands/self/test_sync.py b/tests/console/commands/self/test_sync.py
index 6fdc27fc764..d1c351c74d3 100644
--- a/tests/console/commands/self/test_sync.py
+++ b/tests/console/commands/self/test_sync.py
@@ -6,6 +6,8 @@
 
 from cleo.exceptions import CleoNoSuchOptionError
 
+from poetry.console.commands.self.sync import SelfSyncCommand
+
 # import all tests from the self install command
 # and run them for sync by overriding the command fixture
 from tests.console.commands.self.test_install import *  # noqa: F403
@@ -13,6 +15,7 @@
 
 if TYPE_CHECKING:
     from cleo.testers.command_tester import CommandTester
+    from pytest_mock import MockerFixture
 
 
 @pytest.fixture  # type: ignore[no-redef]
@@ -28,3 +31,15 @@ def test_sync_deprecation() -> None:
 def test_sync_option_not_available(tester: CommandTester) -> None:
     with pytest.raises(CleoNoSuchOptionError):
         tester.execute("--sync")
+
+
+def test_synced_installer(tester: CommandTester, mocker: MockerFixture) -> None:
+    assert isinstance(tester.command, SelfSyncCommand)
+    mock = mocker.patch(
+        "poetry.console.commands.install.InstallCommand.installer",
+        new_callable=mocker.PropertyMock,
+    )
+
+    tester.execute()
+
+    mock.return_value.requires_synchronization.assert_called_with(True)
diff --git a/tests/console/commands/test_sync.py b/tests/console/commands/test_sync.py
index af75afd86f3..89d7e8c7760 100644
--- a/tests/console/commands/test_sync.py
+++ b/tests/console/commands/test_sync.py
@@ -6,6 +6,8 @@
 
 from cleo.exceptions import CleoNoSuchOptionError
 
+from poetry.console.commands.sync import SyncCommand
+
 # import all tests from the install command
 # and run them for sync by overriding the command fixture
 from tests.console.commands.test_install import *  # noqa: F403
@@ -13,6 +15,7 @@
 
 if TYPE_CHECKING:
     from cleo.testers.command_tester import CommandTester
+    from pytest_mock import MockerFixture
 
 
 @pytest.fixture  # type: ignore[no-redef]
@@ -28,3 +31,15 @@ def test_sync_option_is_passed_to_the_installer() -> None:
 def test_sync_option_not_available(tester: CommandTester) -> None:
     with pytest.raises(CleoNoSuchOptionError):
         tester.execute("--sync")
+
+
+def test_synced_installer(tester: CommandTester, mocker: MockerFixture) -> None:
+    assert isinstance(tester.command, SyncCommand)
+    mock = mocker.patch(
+        "poetry.console.commands.install.InstallCommand.installer",
+        new_callable=mocker.PropertyMock,
+    )
+
+    tester.execute()
+
+    mock.return_value.requires_synchronization.assert_called_with(True)
diff --git a/tests/utils/env/test_env.py b/tests/utils/env/test_env.py
index b3f63a7339d..97eda471416 100644
--- a/tests/utils/env/test_env.py
+++ b/tests/utils/env/test_env.py
@@ -309,7 +309,7 @@ def test_env_system_packages_are_relative_to_lib(
 
     # These are the virtual environments' base env packages,
     # in this case the system site packages.
-    for dist in metadata.distributions(path=[str(env.parent_env.site_packages.path)]):
+    for dist in env.parent_env.site_packages.distributions():
         assert (
             env.is_path_relative_to_lib(
                 Path(str(dist._path))  # type: ignore[attr-defined]