diff --git a/src/config.rs b/src/config.rs
index 0db951f..b0ec673 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -32,8 +32,9 @@ impl Config {
                     "Parent zoom level number needs to be bigger than the input image zoom level."
                 )
             }
-            if indexforzoom > (1 << ((parentzoomlevelvalue - zoomlevel) * 2)) - 1 {
-                panic!("indexforzoom value is larger than allowed.")
+            let max_allowed = (1u64 << ((parentzoomlevelvalue - zoomlevel) * 2)) - 1;
+            if (indexforzoom as u64) > max_allowed {
+                panic!("indexforzoom value is larger than allowed.");
             }
             Config {
                 tilesize,
@@ -113,7 +114,7 @@ impl Config {
         }
     }
 
-    pub fn resize_range(&self, img: &DynamicImage) -> Vec<(TileImage, u8)> {
+    pub fn resize_range(&self, img: &DynamicImage) -> Vec<(TileImage<'_>, u8)> {
         <RangeInclusive<u8> as Clone>::clone(&self.zoomrangetoslice)
             .into_par_iter()
             .map(|x: u8| {
@@ -287,6 +288,14 @@ mod tests {
         assert_eq!(config.targetrangetoslice, 0..=1023);
     }
 
+    #[test]
+    // allow indexforzoom values greater than 63 when parent zoom is much larger
+    fn sub_image_large_index() {
+        let config = Config::new(256, 3, Some(7), 212, None, None, Some(2));
+        assert_eq!(config.zoomrangetoslice, 3..=3);
+        assert_eq!(config.targetrangetoslice, 0..=63);
+    }
+
     #[test]
     #[should_panic]
     // should panic if zoomlevel is larger than parentzoomlevel
diff --git a/src/image.rs b/src/image.rs
index 119050f..dee2558 100644
--- a/src/image.rs
+++ b/src/image.rs
@@ -10,18 +10,15 @@ pub struct TileImage<'c> {
 }
 
 impl<'c> TileImage<'c> {
-    pub fn slice_tiles(&self, index: u8) -> Vec<Tile> {
+    pub fn slice_tiles(&self, index: u8) -> Vec<Tile<'_>> {
         let tiles_per_row = 1 << index;
         let morton_idx_max = tiles_per_row * tiles_per_row;
         let tileimage_coord: (u16, u16) = match &self.config.parentzoomlevel {
             None => (0, 0),
-            Some(parentzoomlevel) => {
-                if parentzoomlevel > &self.config.zoomlevel {
-                    coord_of(self.config.indexforzoom.into())
-                } else {
-                    (0, 0)
-                }
+            Some(parentzoomlevel) if parentzoomlevel > &self.config.zoomlevel => {
+                coord_of(self.config.indexforzoom.into())
             }
+            _ => (0, 0),
         };
         let output_level = match &self.config.parentzoomlevel {
             None => index,
diff --git a/src/main.rs b/src/main.rs
index 7d5af58..89dc297 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -75,7 +75,7 @@ fn main() {
     if args.preset.is_some() && &args.tileformat != "png" {
         eprintln!(
             "Error: The --preset argument cannot be used with --tileformat set to '{}'",
-            &args.tileformat
+            args.tileformat
         );
         std::process::exit(2);
     }
@@ -136,7 +136,7 @@ fn main() {
                     let path = &args.output_dir.join(format!(
                         "{name}.{fmt}",
                         name = tile.name,
-                        fmt = &args.tileformat
+                        fmt = args.tileformat
                     ));
                     img.to_image().save(path).unwrap();
                 }