Index: uspace/srv/fs/tmpfs/tmpfs_ops.c
===================================================================
--- uspace/srv/fs/tmpfs/tmpfs_ops.c	(revision 1735f3e4ff366ba52b91d0dc24abe085e1196d7b)
+++ uspace/srv/fs/tmpfs/tmpfs_ops.c	(revision fc2e71e546816f936b7a6de413aba3885f444a5f)
@@ -439,4 +439,5 @@
 {
 	dev_handle_t dev_handle = (dev_handle_t) IPC_GET_ARG1(*request);
+	fs_node_t *rootfn;
 	int rc;
 
@@ -463,4 +464,15 @@
 	opts[size] = '\0';
 
+	/*
+	 * Check if this device is not already mounted.
+	 */
+	rc = tmpfs_root_get(&rootfn, dev_handle);
+	if ((rc == EOK) && (rootfn)) {
+		(void) tmpfs_node_put(&rootfn);
+		free(opts);
+		ipc_answer_0(rid, EEXIST);
+		return;
+	}
+
 	/* Initialize TMPFS instance. */
 	if (!tmpfs_instance_init(dev_handle)) {
@@ -470,5 +482,4 @@
 	}
 
-	fs_node_t *rootfn;
 	rc = tmpfs_root_get(&rootfn, dev_handle);
 	assert(rc == EOK);