diff --git a/nemu/Makefile b/nemu/Makefile
index 4ae01bb..03c8a4e 100644
--- a/nemu/Makefile
+++ b/nemu/Makefile
@@ -69,4 +69,4 @@ all-tests: LDFLAGS += $(shell pkg-config --libs check)
 all-tests: $(TEST_SRCS:%.c=$(OBJ_DIR)/%)
 
 test: all-tests
-	@CK_FORK=0 $(OBJ_DIR)/tests/expr_test
+	@$(OBJ_DIR)/tests/expr_test
diff --git a/nemu/tests/expr_test.c b/nemu/tests/expr_test.c
index 6e37ae2..c20e9c4 100644
--- a/nemu/tests/expr_test.c
+++ b/nemu/tests/expr_test.c
@@ -28,7 +28,7 @@ void gen(char c) {
 }
 
 void gen_num(void) {
-  uint32_t num = rand() % 100000;
+  uint32_t num = rand() % 100;
   int len = 0;
   switch(rand() % 2) {
     case 0: