diff --git a/src/thread/SDL_thread.c b/src/thread/SDL_thread.c
index cf89f958cf..04b0573920 100644
--- a/src/thread/SDL_thread.c
+++ b/src/thread/SDL_thread.c
@@ -99,7 +99,7 @@ bool SDL_SetTLS(SDL_TLSID *id, const void *value, SDL_TLSDestructorCallback dest
 
         oldlimit = storage ? storage->limit : 0;
         newlimit = (storage_index + TLS_ALLOC_CHUNKSIZE);
-        new_storage = (SDL_TLSData *)SDL_realloc(storage, sizeof(*storage) + (newlimit - 1) * sizeof(storage->array[0]));
+        new_storage = (SDL_TLSData *)SDL_realloc(storage, sizeof(*storage) + newlimit * sizeof(storage->array[0]));
         if (!new_storage) {
             return false;
         }
diff --git a/src/thread/SDL_thread_c.h b/src/thread/SDL_thread_c.h
index df73aeb644..3659b85cc4 100644
--- a/src/thread/SDL_thread_c.h
+++ b/src/thread/SDL_thread_c.h
@@ -67,11 +67,18 @@ extern void SDL_RunThread(SDL_Thread *thread);
 typedef struct
 {
     int limit;
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable : 4200) // Flexible array members (C99)
+#endif
     struct
     {
         void *data;
         void(SDLCALL *destructor)(void *);
-    } array[1];
+    } array[];
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
 } SDL_TLSData;
 
 // This is how many TLS entries we allocate at once