diff --git a/Misc/ACKS b/Misc/ACKS
index 41d314e..6f689ad 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -419,6 +419,7 @@
 Lou Kates
 Hiroaki Kawai
 Sebastien Keim
+Ryan Kelly
 Robert Kern
 Randall Kern
 Magnus Kessler
diff --git a/Misc/NEWS b/Misc/NEWS
index ef35ddc..b89f89d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -30,6 +30,9 @@
 Extensions
 ----------
 
+- Issue #6915: Under Windows, os.listdir() didn't release the Global
+  Interpreter Lock around all system calls.  Original patch by Ryan Kelly.
+
 - Issue #8524: Add a detach() method to socket objects, so as to put the
   socket into the closed state without closing the underlying file
   descriptor.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 0b14f5c..449093a 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -1229,7 +1229,7 @@
         /* FILE_FLAG_BACKUP_SEMANTICS is required to open a directory */
         FILE_ATTRIBUTE_NORMAL|FILE_FLAG_BACKUP_SEMANTICS,
         NULL);
-    
+
     if(hFile == INVALID_HANDLE_VALUE) {
         /* Either the target doesn't exist, or we don't have access to
            get a handle to it. If the former, we need to return an error.
@@ -2353,7 +2353,9 @@
             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) {
@@ -2430,7 +2432,9 @@
     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)