diff --git a/PDP11/pdp11_sys.c b/PDP11/pdp11_sys.c
index c8bbb4d9..59dc65d6 100644
--- a/PDP11/pdp11_sys.c
+++ b/PDP11/pdp11_sys.c
@@ -118,8 +118,10 @@ extern DEVICE kmc_dev;
 extern DEVICE uca_dev, ucb_dev;
 extern DEVICE rom_dev;
 extern DEVICE ch_dev;
+#ifdef USE_DISPLAY
 extern DEVICE ng_dev;
 extern DEVICE daz_dev;
+#endif
 extern REG cpu_reg[];
 extern int32 saved_PC;
 
@@ -199,8 +201,10 @@ DEVICE *sim_devices[] = {
     &ke_dev,
     &rom_dev,
     &ch_dev,
+#ifdef USE_DISPLAY
     &ng_dev,
     &daz_dev,
+#endif
 #else
     &clk_dev,
     &tti_dev,