diff --git a/VAX/vax_defs.h b/VAX/vax_defs.h
index 47a9aa18..af1e0988 100644
--- a/VAX/vax_defs.h
+++ b/VAX/vax_defs.h
@@ -379,9 +379,9 @@ extern jmp_buf save_env;
 #define DR_F            0x80                            /* FPD ok flag */
 #define DR_NSPMASK      0x07                            /* #specifiers */
 #define DR_V_USPMASK    4
-#define DR_M_USPMASK    0x07                            /* #spec, sym_ */
-#define DR_GETNSP(x)    ((x) & DR_NSPMASK)
-#define DR_GETUSP(x)    (((x) >> DR_V_USPMASK) & DR_M_USPMASK)
+#define DR_M_USPMASK    0x7                             /* #spec, sym_ */
+#define DR_GETNSP(x)    ((x) & DR_NSPMASK)              /* #specifiers */
+#define DR_GETUSP(x)    (((x) >> DR_V_USPMASK) & DR_M_USPMASK) /* #specifiers for unimplemented instructions */
 
 /* Extra bits in the opcode flag word of the Decode ROM array only for history results */