diff --git a/PDP10/pdp10_defs.h b/PDP10/pdp10_defs.h
index 8737a2ce..aeb51b78 100644
--- a/PDP10/pdp10_defs.h
+++ b/PDP10/pdp10_defs.h
@@ -627,8 +627,8 @@ typedef struct pdp_dib DIB;
 
 /* I/O system parameters */
 
-#define DZ_MUXES        4                               /* max # of muxes */
-#define DZ_LINES        8                               /* lines per mux */
+#define DZ_MUXES        4                               /* default # of muxes */
+#define MAX_DZ_MUXES    4                               /* max # of muxes */
 #define KMC_UNITS       1                               /* max # of KMCs */
 #define INITIAL_KMCS    0                               /* Number initially enabled */
 #define DUP_LINES       4                               /* max # of DUP11's */
diff --git a/PDP11/pdp11_dz.c b/PDP11/pdp11_dz.c
index 3c5f7f61..633ead5d 100644
--- a/PDP11/pdp11_dz.c
+++ b/PDP11/pdp11_dz.c
@@ -78,7 +78,9 @@
 #if !defined (DZ_MUXES)
 #define DZ_MUXES        1
 #endif
+#if !defined (MAX_DZ_MUXES)
 #define MAX_DZ_MUXES    32
+#endif
 #define DZ_LINES        (UNIBUS ? 8 : 4)                /* lines per DZ mux */
 
 #if DZ_MUXES > MAX_DZ_MUXES