diff --git a/src/thread/windows/SDL_systls.c b/src/thread/windows/SDL_systls.c
index f2ef37aff..4c1bd038a 100644
--- a/src/thread/windows/SDL_systls.c
+++ b/src/thread/windows/SDL_systls.c
@@ -29,7 +29,12 @@
 #include "../SDL_thread_c.h"
 
 #if WINAPI_FAMILY_WINRT
+#include <fibersapi.h>
+
+#ifndef TLS_OUT_OF_INDEXES
 #define TLS_OUT_OF_INDEXES  FLS_OUT_OF_INDEXES
+#endif
+
 #define TlsAlloc()  FlsAlloc(NULL)
 #define TlsSetValue FlsSetValue
 #define TlsGetValue FlsGetValue