diff --git a/Lib/distutils/command/sdist.py b/Lib/distutils/command/sdist.py
index 0cc0119..180e286 100644
--- a/Lib/distutils/command/sdist.py
+++ b/Lib/distutils/command/sdist.py
@@ -33,23 +33,6 @@
         "List of available source distribution formats:")
 
 
-def cs_path_exists(fspath):
-    """
-    Case-sensitive path existence check
-
-    >>> cs_path_exists(__file__)
-    True
-    >>> cs_path_exists(__file__.upper())
-    False
-    """
-    if not os.path.exists(fspath):
-        return False
-    # make absolute so we always have a directory
-    abspath = os.path.abspath(fspath)
-    directory, filename = os.path.split(abspath)
-    return filename in os.listdir(directory)
-
-
 class sdist(Command):
 
     description = "create a source distribution (tarball, zip file, etc.)"
@@ -246,6 +229,23 @@
         self._add_defaults_c_libs()
         self._add_defaults_scripts()
 
+    @staticmethod
+    def _cs_path_exists(fspath):
+        """
+        Case-sensitive path existence check
+
+        >>> sdist._cs_path_exists(__file__)
+        True
+        >>> sdist._cs_path_exists(__file__.upper())
+        False
+        """
+        if not os.path.exists(fspath):
+            return False
+        # make absolute so we always have a directory
+        abspath = os.path.abspath(fspath)
+        directory, filename = os.path.split(abspath)
+        return filename in os.listdir(directory)
+
     def _add_defaults_standards(self):
         standards = [self.READMES, self.distribution.script_name]
         for fn in standards:
@@ -253,7 +253,7 @@
                 alts = fn
                 got_it = False
                 for fn in alts:
-                    if cs_path_exists(fn):
+                    if self._cs_path_exists(fn):
                         got_it = True
                         self.filelist.append(fn)
                         break
@@ -262,7 +262,7 @@
                     self.warn("standard file not found: should have one of " +
                               ', '.join(alts))
             else:
-                if cs_path_exists(fn):
+                if self._cs_path_exists(fn):
                     self.filelist.append(fn)
                 else:
                     self.warn("standard file '%s' not found" % fn)