diff --git a/src/animation/common.h b/src/animation/common.h
index 20cfd86..1bbae01 100644
--- a/src/animation/common.h
+++ b/src/animation/common.h
@@ -78,7 +78,7 @@ double find_animation_curve_at(double t, int type) {
 
 double all_output_frame_duration_ms() {
 	int32_t refresh_total = 0;
-	Monitor *m;
+	Monitor *m = NULL;
 	wl_list_for_each(m, &mons, link) {
 		if (!m->wlr_output->enabled) {
 			continue;
diff --git a/src/config/parse_config.h b/src/config/parse_config.h
index 9375005..a56fee1 100644
--- a/src/config/parse_config.h
+++ b/src/config/parse_config.h
@@ -2666,7 +2666,7 @@ void parse_config(void) {
 
 void reapply_monitor_rules(void) {
 	ConfigMonitorRule *mr;
-	Monitor *m;
+	Monitor *m = NULL;
 	int ji, jk;
 	struct wlr_output_state state;
 	struct wlr_output_mode *internal_mode = NULL;
@@ -2766,7 +2766,7 @@ void reapply_pointer(void) {
 void reapply_master(void) {
 
 	int i;
-	Monitor *m;
+	Monitor *m = NULL;
 	for (i = 0; i <= LENGTH(tags); i++) {
 		wl_list_for_each(m, &mons, link) {
 			if (!m->wlr_output->enabled) {
@@ -2784,7 +2784,7 @@ void reapply_master(void) {
 }
 
 void reapply_tagrule(void) {
-	Monitor *m;
+	Monitor *m = NULL;
 	int i, jk;
 	char *rule_monitor_name = NULL;
 	wl_list_for_each(m, &mons, link) {
diff --git a/src/ext-protocol/dwl-ipc.h b/src/ext-protocol/dwl-ipc.h
index b94e902..2705efd 100644
--- a/src/ext-protocol/dwl-ipc.h
+++ b/src/ext-protocol/dwl-ipc.h
@@ -209,7 +209,7 @@ void dwl_ipc_output_set_client_tags(struct wl_client *client,
 									unsigned int and_tags,
 									unsigned int xor_tags) {
 	DwlIpcOutput *ipc_output;
-	Monitor *monitor;
+	Monitor *monitor = NULL;
 	Client *selected_client = NULL;
 	unsigned int newtags = 0;
 
@@ -237,7 +237,7 @@ void dwl_ipc_output_set_layout(struct wl_client *client,
 							   struct wl_resource *resource,
 							   unsigned int index) {
 	DwlIpcOutput *ipc_output;
-	Monitor *monitor;
+	Monitor *monitor = NULL;
 
 	ipc_output = wl_resource_get_user_data(resource);
 	if (!ipc_output)
@@ -256,7 +256,7 @@ void dwl_ipc_output_set_tags(struct wl_client *client,
 							 struct wl_resource *resource, unsigned int tagmask,
 							 unsigned int toggle_tagset) {
 	DwlIpcOutput *ipc_output;
-	Monitor *monitor;
+	Monitor *monitor = NULL;
 	unsigned int newtags = tagmask & TAGMASK;
 
 	ipc_output = wl_resource_get_user_data(resource);
diff --git a/src/ext-protocol/text-input.h b/src/ext-protocol/text-input.h
index 418c660..2fc6b6d 100644
--- a/src/ext-protocol/text-input.h
+++ b/src/ext-protocol/text-input.h
@@ -68,7 +68,7 @@ void dwl_im_relay_set_focus(struct dwl_input_method_relay *relay,
 
 /*------------------协议内部代码------------------------------*/
 Monitor *output_from_wlr_output(struct wlr_output *wlr_output) {
-	Monitor *m;
+	Monitor *m = NULL;
 	wl_list_for_each(m, &mons, link) {
 		if (m->wlr_output == wlr_output) {
 			return m;
@@ -222,7 +222,7 @@ static void update_popup_position(struct dwl_input_method_popup *popup) {
 	struct wlr_xdg_surface *xdg_surface;
 	struct wlr_layer_surface_v1 *layer_surface;
 	struct wlr_scene_tree *tree;
-	Monitor *output;
+	Monitor *output = NULL;
 	struct wlr_xdg_positioner_rules pointer_rules;
 	struct wlr_box output_box;
 	int lx, ly;
diff --git a/src/mango.c b/src/mango.c
index 1a2cfde..fe67814 100644
--- a/src/mango.c
+++ b/src/mango.c
@@ -1064,7 +1064,7 @@ void apply_named_scratchpad(Client *target_client) {
 void gpureset(struct wl_listener *listener, void *data) {
 	struct wlr_renderer *old_drw = drw;
 	struct wlr_allocator *old_alloc = alloc;
-	struct Monitor *m;
+	struct Monitor *m = NULL;
 
 	wlr_log(WLR_DEBUG, "gpu reset");
 
@@ -1235,7 +1235,7 @@ void applyrules(Client *c) {
 	const char *appid, *title;
 	unsigned int i, newtags = 0;
 	const ConfigWinRule *r;
-	Monitor *mon = selmon, *m;
+	Monitor *mon = selmon, *m = NULL;
 	Client *fc = NULL;
 	bool hit_rule_pos = false;
 
@@ -2514,7 +2514,7 @@ void createmon(struct wl_listener *listener, void *data) {
 	unsigned int i;
 	int ji, jk;
 	struct wlr_output_state state;
-	Monitor *m;
+	Monitor *m = NULL;
 	struct wlr_output_mode *internal_mode = NULL;
 	bool custom_monitor_mode = false;
 
@@ -4103,7 +4103,7 @@ void setborder_color(Client *c) {
 
 void exchange_two_client(Client *c1, Client *c2) {
 
-	Monitor *tmp_mon;
+	Monitor *tmp_mon = NULL;
 	unsigned int tmp_tags;
 
 	if (c1 == NULL || c2 == NULL ||
@@ -5141,7 +5141,7 @@ void unmapnotify(struct wl_listener *listener, void *data) {
 	/* Called when the surface is unmapped, and should no longer be shown.
 	 */
 	Client *c = wl_container_of(listener, c, unmap);
-	Monitor *m;
+	Monitor *m = NULL;
 	c->iskilling = 1;
 
 	if (animations && !c->is_clip_to_hide && !c->isminied &&
@@ -5242,7 +5242,7 @@ void updatemons(struct wl_listener *listener, void *data) {
 		wlr_output_configuration_v1_create();
 	Client *c = NULL;
 	struct wlr_output_configuration_head_v1 *config_head;
-	Monitor *m;
+	Monitor *m = NULL;
 	int mon_pos_offsetx, mon_pos_offsety, oldx, oldy;
 
 	/* First remove from the layout the disabled monitors */
@@ -5461,7 +5461,7 @@ toggleseltags:
 }
 
 void view(const Arg *arg, bool want_animation) {
-	Monitor *m;
+	Monitor *m = NULL;
 	if (arg->i) {
 		view_in_mon(arg, want_animation, selmon, true);
 		wl_list_for_each(m, &mons, link) {