diff --git a/src/ids/base32.gleam b/src/ids/base32.gleam
index 12fa183..b053d0e 100644
--- a/src/ids/base32.gleam
+++ b/src/ids/base32.gleam
@@ -8,17 +8,21 @@ import gleam/string
 /// Used by ULID and TypeID
 @internal
 pub fn encode(bytes: BitArray, alphabet: String) -> String {
+  let alphabet_with_index =
+    alphabet
+    |> string.to_graphemes
+    |> list.index_map(fn(x, i) { #(i, x) })
+
   // pad 2 bits because we only supply 128 bits of data but need 130 bits for encoding
-  encode_bytes(<<0:size(2), bytes:bits>>, alphabet)
+  encode_bytes(<<0:size(2), bytes:bits>>, alphabet_with_index)
 }
 
 /// Recursively grabs 5 bits and uses them as index in the alphabet and concatinates them to a string.
-fn encode_bytes(binary: BitArray, alphabet: String) -> String {
+fn encode_bytes(binary: BitArray, alphabet: List(#(Int, String))) -> String {
   case binary {
     <<index:unsigned-size(5), rest:bits>> -> {
       alphabet
-      |> string.to_graphemes
-      |> list.at(index)
+      |> list.key_find(index)
       |> result.unwrap("0")
       |> string.append(encode_bytes(rest, alphabet))
     }