diff --git a/src/modules/backlight.c b/src/modules/backlight.c
index 9f4686d..a72be33 100644
--- a/src/modules/backlight.c
+++ b/src/modules/backlight.c
@@ -466,7 +466,7 @@ static int parse_bus_reply(sd_bus_message *reply, const char *member, void *user
                 r = sd_bus_message_read(reply, "sd", &mon_id, pct);
                 if (r >= 0) {
                     char key[PATH_MAX + 1];
-                    snprintf(key, sizeof(key), "/org/clightd/clightd/Backlight2/%s", mon_id);
+                    make_valid_obj_path(key, sizeof(key), "/org/clightd/clightd/Backlight2", mon_id);
                     map_put(bls, key, pct);
                 }
                 sd_bus_message_exit_container(reply);
diff --git a/src/modules/bus.c b/src/modules/bus.c
index b64448b..b8b86b1 100644
--- a/src/modules/bus.c
+++ b/src/modules/bus.c
@@ -1,5 +1,6 @@
 #include "bus.h"
 #include "utils.h"
+#include <ctype.h>
 
 #define GET_BUS(a)  sd_bus *tmp = a->bus; if (!tmp) { tmp = a->type == USER_BUS ? userbus : sysbus; } if (!tmp) { return -1; }
 
@@ -206,3 +207,17 @@ static int proxy_async_request(struct sd_bus_message *m, void *userdata, sd_bus_
 sd_bus *get_user_bus(void) {
     return userbus;
 }
+
+/*
+ * Build a valid D-Bus object path from root + basename.
+ * Replaces any char not in [A-Za-z0-9_] with '_'.
+ * Mirrors Clightd's make_valid_obj_path in bus_utils.c.
+ */
+void make_valid_obj_path(char *storage, size_t size, const char *root, const char *name) {
+    snprintf(storage, size, "%s/%s", root, name);
+    for (char *p = storage + strlen(root) + 1; *p; p++) {
+        if (!isalnum((unsigned char)*p) && *p != '_') {
+            *p = '_';
+        }
+    }
+}
diff --git a/src/modules/bus.h b/src/modules/bus.h
index 0f8c449..cef05ac 100644
--- a/src/modules/bus.h
+++ b/src/modules/bus.h
@@ -37,7 +37,7 @@ typedef struct {
 #define USERBUS_ARG(name, ...)  USERBUS_ARG_REPLY(name, NULL, NULL, __VA_ARGS__);
 #define SYSBUS_ARG(name, ...)   SYSBUS_ARG_REPLY(name, NULL, NULL, __VA_ARGS__);
 
-
+void make_valid_obj_path(char *storage, size_t size, const char *root, const char *name);
 int call(const bus_args *a, const char *signature, ...);
 int add_match(const bus_args *a, sd_bus_slot **slot, sd_bus_message_handler_t cb);
 int set_property(const bus_args *a, const char *type, const uintptr_t value);
diff --git a/src/modules/wizard.c b/src/modules/wizard.c
index 95a7815..44fea74 100644
--- a/src/modules/wizard.c
+++ b/src/modules/wizard.c
@@ -229,7 +229,7 @@ static int parse_bus_reply(sd_bus_message *reply, const char *member, void *user
             r = sd_bus_message_read(reply, "sd", &sysname, NULL);
             if (r >= 0) {
                 char obj_path[PATH_MAX + 1];
-                snprintf(obj_path, sizeof(obj_path), "/org/clightd/clightd/Backlight2/%s", sysname);
+                make_valid_obj_path(obj_path, sizeof(obj_path), "/org/clightd/clightd/Backlight2", sysname);
                 bl_obj_path = strdup(obj_path);
             }
             sd_bus_message_exit_container(reply);