diff --git a/src/backup/chunk_store.rs b/src/backup/chunk_store.rs
index 5cc944c9..360745d2 100644
--- a/src/backup/chunk_store.rs
+++ b/src/backup/chunk_store.rs
@@ -275,14 +275,13 @@ impl ChunkStore {
     pub fn sweep_unused_chunks(
         &self,
         oldest_writer: i64,
+        phase1_start_time: i64,
         status: &mut GarbageCollectionStatus,
         worker: &WorkerTask,
     ) -> Result<(), Error> {
         use nix::sys::stat::fstatat;
 
-        let now = unsafe { libc::time(std::ptr::null_mut()) };
-
-        let mut min_atime = now - 3600*24; // at least 24h (see mount option relatime)
+        let mut min_atime = phase1_start_time - 3600*24; // at least 24h (see mount option relatime)
 
         if oldest_writer < min_atime {
             min_atime = oldest_writer;
diff --git a/src/backup/datastore.rs b/src/backup/datastore.rs
index a8bb282b..ffd64b81 100644
--- a/src/backup/datastore.rs
+++ b/src/backup/datastore.rs
@@ -492,7 +492,7 @@ impl DataStore {
             self.mark_used_chunks(&mut gc_status, &worker)?;
 
             worker.log("Start GC phase2 (sweep unused chunks)");
-            self.chunk_store.sweep_unused_chunks(oldest_writer, &mut gc_status, &worker)?;
+            self.chunk_store.sweep_unused_chunks(oldest_writer, now, &mut gc_status, &worker)?;
 
             worker.log(&format!("Removed bytes: {}", gc_status.removed_bytes));
             worker.log(&format!("Removed chunks: {}", gc_status.removed_chunks));