diff --git a/AK/Base64.cpp b/AK/Base64.cpp
index 4ed14e0130..35f7934f44 100644
--- a/AK/Base64.cpp
+++ b/AK/Base64.cpp
@@ -56,7 +56,7 @@ static constexpr auto make_lookup_table()
 {
     constexpr auto alphabet = make_alphabet();
     Array<u8, 256> table {};
-    for (size_t i = 0; i < alphabet.size() - 1; ++i) {
+    for (size_t i = 0; i < alphabet.size(); ++i) {
         table[alphabet[i]] = i;
     }
     return table;