diff --git a/nemu/src/monitor/sdb/addrexp.l b/nemu/src/monitor/sdb/addrexp.l
index 979df5a..d294ab8 100644
--- a/nemu/src/monitor/sdb/addrexp.l
+++ b/nemu/src/monitor/sdb/addrexp.l
@@ -9,6 +9,7 @@
 %%
 
 0[xX][0-9a-fA-F]+ { yylval = strtoul(yytext, NULL, 16); return HEX_NUMBER; }
+[0-9]+            { yylval = strtoul(yytext, NULL, 10); return NUMBER; }
 $[a-zA-Z]{2,3}   {
     yylval = isa_reg_str2val(yytext + 1, &success);
     if(!success) {
@@ -16,7 +17,6 @@ $[a-zA-Z]{2,3}   {
         return YYerror;
     }
 }
-[0-9]+            { yylval = strtoul(yytext, NULL, 10); return NUMBER; }
 [+\-*/()]         { return *yytext; }
 [ \t]             {  }
 .                 { printf("Unexpected character: %s\n", yytext); return YYerror; }