diff --git a/nemu/src/monitor/sdb/addrexp.y b/nemu/src/monitor/sdb/addrexp.y
index f429b18..0041088 100644
--- a/nemu/src/monitor/sdb/addrexp.y
+++ b/nemu/src/monitor/sdb/addrexp.y
@@ -25,7 +25,7 @@ expression
     | expression '+' expression { $$ = $1 + $3; }
     | expression '-' expression { $$ = $1 - $3; }
     | expression '*' expression { $$ = $1 * $3; } 
-    | expression '/' expression { $$ = $1 / $3; if($3 == 0) perror("Devide by 0\n"); YYABORT; }
+    | expression '/' expression { $$ = $1 / $3; if($3 == 0) { perror("Devide by 0\n"); YYABORT; }}
     | '-' number { $$ = -$2; }
     | '(' expression ')' { $$ = $2; }
 
diff --git a/nemu/src/monitor/sdb/sdb.c b/nemu/src/monitor/sdb/sdb.c
index be1e25e..e68432b 100644
--- a/nemu/src/monitor/sdb/sdb.c
+++ b/nemu/src/monitor/sdb/sdb.c
@@ -205,7 +205,7 @@ static int cmd_x(char *args) {
   return 0;
 
 wrong_usage:
-  printf("Invalid argument for command x: %s\n", args);
+  printf("Invalid argument for command x: %s\n", arg);
   printf("Usage: x [N: uint] [EXPR: <expr>]\n");
   return 0;
 }