diff --git a/metadata.json b/metadata.json
index 71ea53c..7673722 100644
--- a/metadata.json
+++ b/metadata.json
@@ -1,5 +1,6 @@
 {
   "dependencies": [
-    "github.com/chlorm/elvish-stl"
+    "github.com/chlorm/elvish-stl",
+    "github.com/chlorm/elvish-xdg"
   ]
 }
diff --git a/tmpfs-automount.elv b/tmpfs-automount.elv
index 4195b04..137f496 100644
--- a/tmpfs-automount.elv
+++ b/tmpfs-automount.elv
@@ -20,7 +20,10 @@ use github.com/chlorm/elvish-xdg/xdg
 
 fn main {
     # Make sure XDG_RUNTIME_DIR is configured.
-    local:capture = (xdg:get-dir XDG_RUNTIME_DIR)
+    local:run = (xdg:get-dir XDG_RUNTIME_DIR)
+    if (not (==s (get-env XDG_RUNTIME_DIR) $run)) {
+        set-env XDG_RUNTIME_DIR $run
+    }
 
     local:mount-cache = $false
     try {