diff -Naur a/mozilla/nsprpub/pr/src/pthreads/ptio.c b/mozilla/nsprpub/pr/src/pthreads/ptio.c
--- a/mozilla/nsprpub/pr/src/pthreads/ptio.c	2017-07-25 16:58:21.471397566 -0700
+++ b/mozilla/nsprpub/pr/src/pthreads/ptio.c 	2017-07-25 16:58:07.367175478 -0700
@@ -3411,6 +3411,12 @@
     return fd;
 }  /* PR_AllocFileDesc */
 
+PR_IMPLEMENT(void) PR_FreeFileDesc(PRFileDesc *fd)
+{
+    PR_ASSERT(fd);
+    _PR_Putfd(fd);
+}
+
 #if !defined(_PR_INET6) || defined(_PR_INET6_PROBE)
 PR_EXTERN(PRStatus) _pr_push_ipv6toipv4_layer(PRFileDesc *fd);
 #if defined(_PR_INET6_PROBE)
diff -Naur a/mozilla/nsprpub/pr/src/nspr.def b/mozilla/nsprpub/pr/src/nspr.def
--- a/mozilla/nsprpub/pr/src/nspr.def	2009-03-18 14:29:31.000000000 -0700
+++ b/mozilla/nsprpub/pr/src/nspr.def 	2017-07-25 17:06:39.035233443 -0700
@@ -167,6 +167,7 @@
 		PR_FindNextTraceRname;
 		PR_FormatTimeUSEnglish;
 		PR_Free;
+		PR_FreeFileDesc;
 		PR_FreeLibraryName;
 		PR_GMTParameters;
 		PR_GetConnectStatus;