diff --git a/include/sys/sysmacros.h b/include/sys/sysmacros.h
index 1ac49b4f0c..e73c7fd1e8 100644
--- a/include/sys/sysmacros.h
+++ b/include/sys/sysmacros.h
@@ -95,8 +95,12 @@
 #define minclsyspri			(MAX_RT_PRIO)
 #define maxclsyspri			(MAX_PRIO-1)
 
+#ifndef NICE_TO_PRIO
 #define NICE_TO_PRIO(nice)		(MAX_RT_PRIO + (nice) + 20)
+#endif
+#ifndef PRIO_TO_NICE
 #define PRIO_TO_NICE(prio)		((prio) - MAX_RT_PRIO - 20)
+#endif
 
 /* Missing macros
  */