diff --git a/src/api2/admin/datastore/backup/environment.rs b/src/api2/admin/datastore/backup/environment.rs
index cffa555b..af580b69 100644
--- a/src/api2/admin/datastore/backup/environment.rs
+++ b/src/api2/admin/datastore/backup/environment.rs
@@ -231,9 +231,18 @@ impl BackupEnvironment {
         };
 
         if data.chunk_count != chunk_count {
-            bail!("fixed writer '{}' close failed - unexpected chunk count ({} != {})", data.name, data.chunk_count, chunk_count);
+            bail!("fixed writer '{}' close failed - received wrong number of chunk ({} != {})", data.name, data.chunk_count, chunk_count);
         }
 
+        let expected_count = data.index.index_length();
+
+        if chunk_count != (expected_count as u64) {
+            bail!("fixed writer '{}' close failed - unexpected chunk count ({} != {})", data.name, expected_count, chunk_count);
+        }
+
+        if size != (data.size as u64) {
+            bail!("fixed writer '{}' close failed - unexpected file size ({} != {})", data.name, data.size, size);
+        }
 
         data.index.close()?;
 
diff --git a/src/backup/fixed_index.rs b/src/backup/fixed_index.rs
index 8f664d7f..be599a34 100644
--- a/src/backup/fixed_index.rs
+++ b/src/backup/fixed_index.rs
@@ -278,6 +278,10 @@ impl FixedIndexWriter {
         })
     }
 
+    pub fn index_length(&self) -> usize {
+        self.index_length
+    }
+
     fn unmap(&mut self) -> Result<(), Error> {
 
         if self.index == std::ptr::null_mut() { return Ok(()); }
@@ -354,7 +358,6 @@ impl FixedIndexWriter {
     }
 
     pub fn add_digest(&mut self, index: usize, digest: &[u8; 32]) -> Result<(), Error> {
-
         if index >= self.index_length {
             bail!("add digest failed - index out of range ({} >= {})", index, self.index_length);
         }