diff --git a/sphinx/ext/viewcode.py b/sphinx/ext/viewcode.py
index ebfe4322f84..b64d67bdad3 100644
--- a/sphinx/ext/viewcode.py
+++ b/sphinx/ext/viewcode.py
@@ -29,6 +29,7 @@
     from sphinx.application import Sphinx
     from sphinx.builders import Builder
     from sphinx.environment import BuildEnvironment
+    from sphinx.util._pathlib import _StrPath
     from sphinx.util.typing import ExtensionMetadata
 
 logger = logging.getLogger(__name__)
@@ -207,7 +208,7 @@ def remove_viewcode_anchors(self) -> None:
             node.parent.remove(node)
 
 
-def get_module_filename(app: Sphinx, modname: str) -> str | None:
+def get_module_filename(app: Sphinx, modname: str) -> _StrPath | None:
     """Get module filename for *modname*."""
     source_info = app.emit_firstresult('viewcode-find-source', modname)
     if source_info:
diff --git a/sphinx/pycode/__init__.py b/sphinx/pycode/__init__.py
index 81f0519a5a1..0242cf9c8be 100644
--- a/sphinx/pycode/__init__.py
+++ b/sphinx/pycode/__init__.py
@@ -2,8 +2,6 @@
 
 from __future__ import annotations
 
-import os
-import os.path
 import tokenize
 from importlib import import_module
 from typing import TYPE_CHECKING, Any, Literal
@@ -13,6 +11,7 @@
 from sphinx.util._pathlib import _StrPath
 
 if TYPE_CHECKING:
+    import os
     from inspect import Signature
 
 
@@ -28,7 +27,7 @@ class ModuleAnalyzer:
     cache: dict[tuple[Literal['file', 'module'], str | _StrPath], Any] = {}
 
     @staticmethod
-    def get_module_source(modname: str) -> tuple[str | None, str | None]:
+    def get_module_source(modname: str) -> tuple[_StrPath | None, str | None]:
         """Try to find the source code for a module.
 
         Returns ('filename', 'source'). One of it can be None if
@@ -39,14 +38,15 @@ def get_module_source(modname: str) -> tuple[str | None, str | None]:
         except Exception as err:
             raise PycodeError('error importing %r' % modname, err) from err
         loader = getattr(mod, '__loader__', None)
-        filename = getattr(mod, '__file__', None)
+        filename: str | None = getattr(mod, '__file__', None)
         if loader and getattr(loader, 'get_source', None):
             # prefer Native loader, as it respects #coding directive
             try:
                 source = loader.get_source(modname)
                 if source:
+                    mod_path = None if filename is None else _StrPath(filename)
                     # no exception and not None - it must be module source
-                    return filename, source
+                    return mod_path, source
             except ImportError:
                 pass  # Try other "source-mining" methods
         if filename is None and loader and getattr(loader, 'get_filename', None):
@@ -60,24 +60,28 @@ def get_module_source(modname: str) -> tuple[str | None, str | None]:
         if filename is None:
             # all methods for getting filename failed, so raise...
             raise PycodeError('no source found for module %r' % modname)
-        filename = os.path.normpath(os.path.abspath(filename))
-        if filename.lower().endswith(('.pyo', '.pyc')):
-            filename = filename[:-1]
-            if not os.path.isfile(filename) and os.path.isfile(filename + 'w'):
-                filename += 'w'
-        elif not filename.lower().endswith(('.py', '.pyw')):
-            raise PycodeError('source is not a .py file: %r' % filename)
-
-        if not os.path.isfile(filename):
-            raise PycodeError('source file is not present: %r' % filename)
-        return filename, None
+        mod_path = _StrPath(filename).resolve()
+        if mod_path.suffix in {'.pyo', '.pyc'}:
+            mod_path_pyw = mod_path.with_suffix('.pyw')
+            if not mod_path.is_file() and mod_path_pyw.is_file():
+                mod_path = mod_path_pyw
+            else:
+                mod_path = mod_path.with_suffix('.py')
+        elif mod_path.suffix not in {'.py', '.pyw'}:
+            msg = f'source is not a .py file: {mod_path!r}'
+            raise PycodeError(msg)
+
+        if not mod_path.is_file():
+            msg = f'source file is not present: {mod_path!r}'
+            raise PycodeError(msg)
+        return mod_path, None
 
     @classmethod
     def for_string(
         cls: type[ModuleAnalyzer],
         string: str,
         modname: str,
-        srcname: str = '<string>',
+        srcname: str | os.PathLike[str] = '<string>',
     ) -> ModuleAnalyzer:
         return cls(string, modname, srcname)