diff --git a/src/core/path.c b/src/core/path.c
index 8a5ec0a72f6..1893d8de458 100644
--- a/src/core/path.c
+++ b/src/core/path.c
@@ -80,7 +80,8 @@ int path_spec_watch(PathSpec *s, sd_event_io_handler_t handler) {
 
         (void) sd_event_source_set_description(s->event_source, "path");
 
-        /* This assumes the path was passed through path_kill_slashes()! */
+        /* This function assumes the path was passed through path_kill_slashes()! */
+        assert(!strstr(s->path, "//"));
 
         for (slash = strchr(s->path, '/'); ; slash = strchr(slash+1, '/')) {
                 char *cut = NULL;