diff --git a/tests/libtest/lib3207.c b/tests/libtest/lib3207.c
index 446d98a000..040e802511 100644
--- a/tests/libtest/lib3207.c
+++ b/tests/libtest/lib3207.c
@@ -68,7 +68,11 @@ static size_t write_memory_callback(char *contents, size_t size,
   return realsize;
 }
 
+#if defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32)
 static CURL_THREAD_RETURN_T CURL_STDCALL test_thread(void *ptr)
+#else
+static void test_thread(void *ptr)
+#endif
 {
   struct Ctx *ctx = (struct Ctx *)ptr;
   CURLcode res = CURLE_OK;