diff --git a/test/rt/configuration.xml b/test/rt/configuration.xml
index c8db1d1a3..9abba49f2 100644
--- a/test/rt/configuration.xml
+++ b/test/rt/configuration.xml
@@ -41,7 +41,11 @@
             <value><![CDATA[/*
  * Allowed delay in timeout checks.
  */
-#define ALLOWED_DELAY TIME_MS2I(2)
+#if CH_CFG_ST_TIMEDELTA == 0
+#define ALLOWED_DELAY           2
+#else
+#define ALLOWED_DELAY           CH_CFG_ST_TIMEDELTA
+#endif
 
 /*
  * Maximum number of test threads.
diff --git a/test/rt/source/test/rt_test_root.h b/test/rt/source/test/rt_test_root.h
index 9bda53b1a..89fe90a0b 100644
--- a/test/rt/source/test/rt_test_root.h
+++ b/test/rt/source/test/rt_test_root.h
@@ -59,7 +59,11 @@ extern "C" {
 /*
  * Allowed delay in timeout checks.
  */
-#define ALLOWED_DELAY TIME_MS2I(2)
+#if CH_CFG_ST_TIMEDELTA == 0
+#define ALLOWED_DELAY           2
+#else
+#define ALLOWED_DELAY           CH_CFG_ST_TIMEDELTA
+#endif
 
 /*
  * Maximum number of test threads.