diff --git a/test/test_iomux.c b/test/test_iomux.c
index 303a284..bc150e9 100644
--- a/test/test_iomux.c
+++ b/test/test_iomux.c
@@ -8,12 +8,12 @@
 
 static enum IOMUX_TYPE g_iomux_type = IOMUX_TYPE_DEFAULT;
 
-void set_iomux_type_select(void)
+static void set_iomux_type_select(void)
 {
     g_iomux_type = IOMUX_TYPE_SELECT;
 }
 
-void set_iomux_type_epoll(void)
+static void set_iomux_type_epoll(void)
 {
     g_iomux_type = IOMUX_TYPE_EPOLL;
 }