diff --git a/src/with_indices.rs b/src/with_indices.rs
index a602902..465aa73 100644
--- a/src/with_indices.rs
+++ b/src/with_indices.rs
@@ -9,7 +9,7 @@ where
 {
   /// line is a string reference
   pub line: S,
-  last_char_index_to_byte_index: RefCell<(u32, u32)>,
+  char_index_to_byte_index: RefCell<[(u32, u32); 2]>,
   data: PhantomData<&'a S>,
 }
 
@@ -20,7 +20,7 @@ where
   pub fn new(line: S) -> Self {
     Self {
       line,
-      last_char_index_to_byte_index: RefCell::new((0, 0)),
+      char_index_to_byte_index: RefCell::new([(0, 0), (0, 0)]),
       data: PhantomData,
     }
   }
@@ -39,40 +39,54 @@ where
     let mut start_byte_index = None;
     let mut end_byte_index = None;
 
-    let (last_char_index, last_byte_index) =
-      *self.last_char_index_to_byte_index.borrow();
-    let mut last_byte_index = last_byte_index as usize;
-    let mut char_index = last_char_index as usize;
-    if start_char_index < last_char_index as usize {
-      char_index = 0;
-      last_byte_index = 0;
+    let mut current_char_index = 0;
+    let mut current_byte_index = 0;
+    for (last_char_index, last_byte_index) in
+      *self.char_index_to_byte_index.borrow()
+    {
+      if start_char_index >= last_char_index as usize {
+        current_char_index = last_char_index as usize;
+        current_byte_index = last_byte_index as usize;
+      }
     }
+
     for (byte_index, _) in self
       .line
-      .byte_slice(last_byte_index..line_len)
+      .byte_slice(current_byte_index..line_len)
       .char_indices()
     {
-      if char_index == start_char_index {
-        start_byte_index = Some(byte_index + last_byte_index);
+      if current_char_index == start_char_index {
+        start_byte_index = Some(byte_index + current_byte_index);
         if end_char_index == usize::MAX {
           break;
         }
       }
-      if char_index == end_char_index {
-        end_byte_index = Some(byte_index + last_byte_index);
-        *self.last_char_index_to_byte_index.borrow_mut() =
-          (end_char_index as u32, (byte_index + last_byte_index) as u32);
+      if current_char_index == end_char_index {
+        end_byte_index = Some(byte_index + current_byte_index);
         break;
       }
-      char_index += 1;
+      current_char_index += 1;
     }
 
+    let mut char_index_to_byte_index =
+      *self.char_index_to_byte_index.borrow_mut();
     let start_byte_index = if let Some(start_byte_index) = start_byte_index {
+      char_index_to_byte_index[0] =
+        (start_char_index as u32, start_byte_index as u32);
       start_byte_index
     } else {
+      char_index_to_byte_index[0] = (0, 0);
       return S::default();
     };
-    let end_byte_index = end_byte_index.unwrap_or(line_len);
+
+    let end_byte_index = if let Some(end_byte_index) = end_byte_index {
+      char_index_to_byte_index[1] =
+        (end_char_index as u32, end_byte_index as u32);
+      end_byte_index
+    } else {
+      char_index_to_byte_index[0] = (0, 0);
+      line_len
+    };
 
     #[allow(unsafe_code)]
     unsafe {