diff --git a/Lib/imp.py b/Lib/imp.py
index 58d1c97..419f631 100644
--- a/Lib/imp.py
+++ b/Lib/imp.py
@@ -13,7 +13,7 @@
 
 # Directly exposed by this module
 from importlib._bootstrap import new_module
-from importlib._bootstrap import cache_from_source
+from importlib._bootstrap import cache_from_source, source_from_cache
 
 
 from importlib import _bootstrap
@@ -58,29 +58,6 @@
     return extensions + source + bytecode
 
 
-def source_from_cache(path):
-    """Given the path to a .pyc./.pyo file, return the path to its .py file.
-
-    The .pyc/.pyo file does not need to exist; this simply returns the path to
-    the .py file calculated to correspond to the .pyc/.pyo file.  If path does
-    not conform to PEP 3147 format, ValueError will be raised. If
-    sys.implementation.cache_tag is None then NotImplementedError is raised.
-
-    """
-    if sys.implementation.cache_tag is None:
-        raise NotImplementedError('sys.implementation.cache_tag is None')
-    head, pycache_filename = os.path.split(path)
-    head, pycache = os.path.split(head)
-    if pycache != _bootstrap._PYCACHE:
-        raise ValueError('{} not bottom-level directory in '
-                         '{!r}'.format(_bootstrap._PYCACHE, path))
-    if pycache_filename.count('.') != 2:
-        raise ValueError('expected only 2 dots in '
-                         '{!r}'.format(pycache_filename))
-    base_filename = pycache_filename.partition('.')[0]
-    return os.path.join(head, base_filename + machinery.SOURCE_SUFFIXES[0])
-
-
 class NullImporter:
 
     """Null import object."""