diff --git a/B5500/b5500_cpu.c b/B5500/b5500_cpu.c
index db301cfd..6dcb50d4 100644
--- a/B5500/b5500_cpu.c
+++ b/B5500/b5500_cpu.c
@@ -3958,9 +3958,7 @@ cpu_show_hist(FILE * st, UNIT * uptr, int32 val, CONST void *desc)
     t_stat              r;
     t_value             sim_eval;
     struct InstHistory *h;
-    extern void         print_opcode(FILE * ofile, t_value val, t_opcode *);
-    extern t_opcode     word_ops[1], char_ops[1];
-    char                flags[] = "ABCNSMV";
+    static const char   flags[] = "ABCNSMV";
 
     if (hst_lnt == 0)
         return SCPE_NOFNC;      /* enabled? */
diff --git a/B5500/b5500_defs.h b/B5500/b5500_defs.h
index 9f11639d..7877be01 100644
--- a/B5500/b5500_defs.h
+++ b/B5500/b5500_defs.h
@@ -72,6 +72,8 @@ typedef struct _opcode
 }
 t_opcode;
 
+extern void         print_opcode(FILE * ofile, t_value val, t_opcode *);
+extern t_opcode     word_ops[], char_ops[];
 
 t_stat chan_reset(DEVICE *);
 t_stat chan_boot(t_uint64);