diff --git a/sys/kern/subr_bus.c b/sys/kern/subr_bus.c
--- a/sys/kern/subr_bus.c
+++ b/sys/kern/subr_bus.c
@@ -624,7 +624,12 @@
 devclass_t
 devclass_create(const char *classname)
 {
-	return (devclass_find_internal(classname, NULL, TRUE));
+	devclass_t rv;
+
+	bus_topo_lock();
+	rv = devclass_find_internal(classname, NULL, TRUE);
+	bus_topo_unlock();
+	return (rv);
 }
 
 /**
@@ -638,7 +643,12 @@
 devclass_t
 devclass_find(const char *classname)
 {
-	return (devclass_find_internal(classname, NULL, FALSE));
+	devclass_t rv;
+
+	bus_topo_lock();
+	rv = devclass_find_internal(classname, NULL, FALSE);
+	bus_topo_unlock();
+	return (rv);
 }
 
 /**