diff --git a/CoreFoundation/Base.subproj/CFPlatform.c b/CoreFoundation/Base.subproj/CFPlatform.c
index 343eb93d1c..f20c6be720 100644
--- a/CoreFoundation/Base.subproj/CFPlatform.c
+++ b/CoreFoundation/Base.subproj/CFPlatform.c
@@ -580,11 +580,16 @@ CF_PRIVATE void __CFFinalizeWindowsThreadData() {
 #endif
 
 static pthread_key_t __CFTSDIndexKey;
+static pthread_once_t __CFTSDIndexKey_once = PTHREAD_ONCE_INIT;
 
-CF_PRIVATE void __CFTSDInitialize() {
+CF_PRIVATE void __CFTSDInitializeOnce() {
     (void)pthread_key_create(&__CFTSDIndexKey, __CFTSDFinalize);
 }
 
+CF_PRIVATE void __CFTSDInitialize() {
+    (void)pthread_once(&__CFTSDIndexKey_once, __CFTSDInitializeOnce);
+}
+
 static void __CFTSDSetSpecific(void *arg) {
 #if DEPLOYMENT_TARGET_MACOSX || DEPLOYMENT_TARGET_EMBEDDED || DEPLOYMENT_TARGET_EMBEDDED_MINI
     pthread_setspecific(__CFTSDIndexKey, arg);