diff --git a/Misc/ACKS b/Misc/ACKS
index 67684eb539e..1b3f0d50a9c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -398,6 +398,7 @@ Jacob Kaplan-Moss
 Lou Kates
 Hiroaki Kawai
 Sebastien Keim
+Ryan Kelly
 Robert Kern
 Randall Kern
 Magnus Kessler
diff --git a/Misc/NEWS b/Misc/NEWS
index 9e2603d5cec..a79e4cd8b65 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -98,6 +98,9 @@ C-API
 Library
 -------
 
+- Issue #6915: Under Windows, os.listdir() didn't release the Global
+  Interpreter Lock around all system calls.  Original patch by Ryan Kelly.
+
 - Issue #3757: thread-local objects now support cyclic garbage collection.
   Thread-local objects involved in reference cycles will be deallocated
   timely by the cyclic GC, even if the underlying thread is still running.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index cb3075bdbc9..d6e491cc969 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -2270,7 +2270,9 @@ posix_listdir(PyObject *self, PyObject *args)
                 free(wnamebuf);
                 return NULL;
             }
+            Py_BEGIN_ALLOW_THREADS
             hFindFile = FindFirstFileW(wnamebuf, &wFileData);
+            Py_END_ALLOW_THREADS
             if (hFindFile == INVALID_HANDLE_VALUE) {
                 int error = GetLastError();
                 if (error == ERROR_FILE_NOT_FOUND) {
@@ -2348,7 +2350,9 @@ posix_listdir(PyObject *self, PyObject *args)
     if ((d = PyList_New(0)) == NULL)
         return NULL;
 
+    Py_BEGIN_ALLOW_THREADS
     hFindFile = FindFirstFile(namebuf, &FileData);
+    Py_END_ALLOW_THREADS
     if (hFindFile == INVALID_HANDLE_VALUE) {
         int error = GetLastError();
         if (error == ERROR_FILE_NOT_FOUND)