diff --git a/control/compute_z.h b/control/compute_z.h
index 7a1086edc9b5b223d1a020f85475e4142141b931..5ea23598df07fb7327a18a1613fcb5c5bbaac182 100644
--- a/control/compute_z.h
+++ b/control/compute_z.h
@@ -33,7 +33,7 @@
  **/
 #define MorseDescInput  1
 #define MorseDescOutput 2
-#define MorseDescInout  3
+#define MorseDescInout  (MorseDescInput | MorseDescOutput)
 
 /***************************************************************************//**
  *  Macro for matrix conversion / Lapack interface