--- a/tests/test_properties.c	Tue Dec 23 10:14:13 2025 +0100
+++ b/tests/test_properties.c	Tue Dec 23 14:31:56 2025 +0100
@@ -492,7 +492,7 @@
 }
 
 static FILE *cx_opentmp(char *tpl) {
-#if defined _POSIX_C_SOURCE && _POSIX_C_SOURCE >= 200809L
+#ifdef WITH_MKSTEMP
     strcpy(tpl, "ucxtestXXXXXX");
     int fd = mkstemp(tpl);
     if (fd < 0) return NULL;