diff --git a/src/commands.rs b/src/commands.rs
index bf1b872..22e7135 100644
--- a/src/commands.rs
+++ b/src/commands.rs
@@ -218,7 +218,7 @@ pub(crate) async fn register_image(
 
             match index {
                 Some(index) => {
-                    let index_size = ((device_size + chunk_size - 1) / chunk_size) as usize;
+                    let index_size = device_size.div_ceil(chunk_size) as usize;
                     if index_size != index.index_count() {
                         bail!("previous backup has different size than current state, cannot do incremental backup (drive: {})", archive_name);
                     }
diff --git a/src/upload_queue.rs b/src/upload_queue.rs
index 261886c..e0737da 100644
--- a/src/upload_queue.rs
+++ b/src/upload_queue.rs
@@ -91,7 +91,7 @@ async fn upload_handler(
     let mut digest_list = Vec::new();
     let mut offset_list = Vec::new();
 
-    let index_size = ((device_size + chunk_size - 1) / chunk_size) as usize;
+    let index_size = device_size.div_ceil(chunk_size) as usize;
     let mut index = Vec::with_capacity(index_size);
     index.resize(index_size, [0u8; 32]);