diff --git a/nemu/src/monitor/sdb/addrexp.y b/nemu/src/monitor/sdb/addrexp.y
index f83733d..815c7b5 100644
--- a/nemu/src/monitor/sdb/addrexp.y
+++ b/nemu/src/monitor/sdb/addrexp.y
@@ -16,6 +16,7 @@
 
 %token NUMBER HEX_NUMBER
 %token REGISTER
+%locations
 %start input
 %define api.value.type { word_t }
 %parse-param { uint32_t *result }
diff --git a/nemu/tests/expr_test.c b/nemu/tests/expr_test.c
index 59ed3d3..038294a 100644
--- a/nemu/tests/expr_test.c
+++ b/nemu/tests/expr_test.c
@@ -176,6 +176,7 @@ START_TEST(test_expr_plain_register) {
     fputs(buf, stderr);
     gpr(i) = i;
   }
+
   yy_scan_string(buf);
   uint32_t value;
   ck_assert(!yyparse(&value));