diff --git a/src/core/mount.c b/src/core/mount.c
index 477c2cbafa..9f7b490401 100644
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -1782,7 +1782,7 @@ fail:
 }
 
 static int mount_dispatch_io(sd_event_source *source, int fd, uint32_t revents, void *userdata) {
-        _cleanup_set_free_ Set *around = NULL, *gone = NULL;
+        _cleanup_set_free_free_ Set *around = NULL, *gone = NULL;
         Manager *m = userdata;
         const char *what;
         Iterator i;
@@ -1843,7 +1843,7 @@ static int mount_dispatch_io(sd_event_source *source, int fd, uint32_t revents,
 
                                 /* Remember that this device might just have disappeared */
                                 if (set_ensure_allocated(&gone, &path_hash_ops) < 0 ||
-                                    set_put(gone, mount->parameters_proc_self_mountinfo.what) < 0)
+                                    set_put_strdup(gone, mount->parameters_proc_self_mountinfo.what) < 0)
                                         log_oom(); /* we don't care too much about OOM here... */
                         }
 
@@ -1896,9 +1896,10 @@ static int mount_dispatch_io(sd_event_source *source, int fd, uint32_t revents,
                 if (mount_is_mounted(mount) &&
                     mount->from_proc_self_mountinfo &&
                     mount->parameters_proc_self_mountinfo.what) {
+                        /* Track devices currently used */
 
                         if (set_ensure_allocated(&around, &path_hash_ops) < 0 ||
-                            set_put(around, mount->parameters_proc_self_mountinfo.what) < 0)
+                            set_put_strdup(around, mount->parameters_proc_self_mountinfo.what) < 0)
                                 log_oom();
                 }