diff --git a/src/api2/backup.rs b/src/api2/backup.rs
index 4b019007..f541eb97 100644
--- a/src/api2/backup.rs
+++ b/src/api2/backup.rs
@@ -106,7 +106,7 @@ async move {
         }
     }
 
-    let (path, is_new) = datastore.create_backup_dir(&backup_dir)?;
+    let (path, is_new, _snap_guard) = datastore.create_locked_backup_dir(&backup_dir)?;
     if !is_new { bail!("backup directory already exists."); }
 
     WorkerTask::spawn("backup", Some(worker_id), userid.clone(), true, move |worker| {
@@ -146,6 +146,7 @@ async move {
         async move {
             // keep flock until task ends
             let _group_guard = _group_guard;
+            let _snap_guard = _snap_guard;
 
             let res = select!{
                 req = req_fut => req,
diff --git a/src/backup/datastore.rs b/src/backup/datastore.rs
index 71544d20..37f581bc 100644
--- a/src/backup/datastore.rs
+++ b/src/backup/datastore.rs
@@ -334,15 +334,20 @@ impl DataStore {
     /// Creates a new backup snapshot inside a BackupGroup
     ///
     /// The BackupGroup directory needs to exist.
-    pub fn create_backup_dir(&self, backup_dir: &BackupDir) ->  Result<(PathBuf, bool), io::Error> {
+    pub fn create_locked_backup_dir(&self, backup_dir: &BackupDir)
+        -> Result<(PathBuf, bool, DirLockGuard), Error>
+    {
         let relative_path = backup_dir.relative_path();
         let mut full_path = self.base_path();
         full_path.push(&relative_path);
 
+        let lock = ||
+            lock_dir_noblock(&full_path, "snapshot", "internal error - tried creating snapshot that's already in use");
+
         match std::fs::create_dir(&full_path) {
-            Ok(_) => Ok((relative_path, true)),
-            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => Ok((relative_path, false)),
-            Err(e) => Err(e)
+            Ok(_) => Ok((relative_path, true, lock()?)),
+            Err(ref e) if e.kind() == io::ErrorKind::AlreadyExists => Ok((relative_path, false, lock()?)),
+            Err(e) => Err(e.into())
         }
     }
 
diff --git a/src/client/pull.rs b/src/client/pull.rs
index 05b7c66c..2428051a 100644
--- a/src/client/pull.rs
+++ b/src/client/pull.rs
@@ -297,7 +297,7 @@ pub async fn pull_snapshot_from(
     snapshot: &BackupDir,
 ) -> Result<(), Error> {
 
-    let (_path, is_new) = tgt_store.create_backup_dir(&snapshot)?;
+    let (_path, is_new, _snap_lock) = tgt_store.create_locked_backup_dir(&snapshot)?;
 
     if is_new {
         worker.log(format!("sync snapshot {:?}", snapshot.relative_path()));