diff --git a/Libraries/LibRegex/RegexParser.cpp b/Libraries/LibRegex/RegexParser.cpp
index 128ddb14b75..e45b9c95a2e 100644
--- a/Libraries/LibRegex/RegexParser.cpp
+++ b/Libraries/LibRegex/RegexParser.cpp
@@ -11,6 +11,7 @@
 #include <AK/ByteString.h>
 #include <AK/CharacterTypes.h>
 #include <AK/Debug.h>
+#include <AK/DeprecatedFlyString.h>
 #include <AK/GenericLexer.h>
 #include <AK/ScopeGuard.h>
 #include <AK/StringBuilder.h>
@@ -981,7 +982,7 @@ bool ECMA262Parser::parse_pattern(ByteCode& stack, size_t& match_length_minimum,
     return parse_disjunction(stack, match_length_minimum, flags);
 }
 
-bool ECMA262Parser::has_duplicate_in_current_alternative(ByteString const& name)
+bool ECMA262Parser::has_duplicate_in_current_alternative(DeprecatedFlyString const& name)
 {
     auto it = m_parser_state.named_capture_groups.find(name);
     if (it == m_parser_state.named_capture_groups.end())
@@ -2502,7 +2503,7 @@ bool ECMA262Parser::parse_unicode_property_escape(PropertyEscape& property, bool
         [](Empty&) -> bool { VERIFY_NOT_REACHED(); });
 }
 
-ByteString ECMA262Parser::read_capture_group_specifier(bool take_starting_angle_bracket)
+DeprecatedFlyString ECMA262Parser::read_capture_group_specifier(bool take_starting_angle_bracket)
 {
     static constexpr u32 const REPLACEMENT_CHARACTER = 0xFFFD;
     constexpr u32 const ZERO_WIDTH_NON_JOINER { 0x200C };
@@ -2603,7 +2604,7 @@ ByteString ECMA262Parser::read_capture_group_specifier(bool take_starting_angle_
         builder.append_code_point(code_point);
     }
 
-    auto name = builder.to_byte_string();
+    DeprecatedFlyString name = builder.to_byte_string();
     if (!hit_end || name.is_empty())
         set_error(Error::InvalidNameForCaptureGroup);
 
diff --git a/Libraries/LibRegex/RegexParser.h b/Libraries/LibRegex/RegexParser.h
index 517337426fd..eb8a8bce8be 100644
--- a/Libraries/LibRegex/RegexParser.h
+++ b/Libraries/LibRegex/RegexParser.h
@@ -59,7 +59,7 @@ public:
         size_t match_length_minimum;
         Error error;
         Token error_token;
-        Vector<ByteString> capture_groups;
+        Vector<DeprecatedFlyString> capture_groups;
         AllOptions options;
 
         struct {
@@ -117,7 +117,7 @@ protected:
         size_t repetition_mark_count { 0 };
         AllOptions regex_options;
         HashMap<size_t, size_t> capture_group_minimum_lengths;
-        HashMap<ByteString, Vector<NamedCaptureGroup>> named_capture_groups;
+        HashMap<DeprecatedFlyString, Vector<NamedCaptureGroup>> named_capture_groups;
 
         explicit ParserState(Lexer& lexer)
             : lexer(lexer)
@@ -240,7 +240,7 @@ private:
     };
     StringView read_digits_as_string(ReadDigitsInitialZeroState initial_zero = ReadDigitsInitialZeroState::Allow, bool hex = false, int max_count = -1, int min_count = -1);
     Optional<unsigned> read_digits(ReadDigitsInitialZeroState initial_zero = ReadDigitsInitialZeroState::Allow, bool hex = false, int max_count = -1, int min_count = -1);
-    ByteString read_capture_group_specifier(bool take_starting_angle_bracket = false);
+    DeprecatedFlyString read_capture_group_specifier(bool take_starting_angle_bracket = false);
 
     struct Script {
         Unicode::Script script {};
@@ -282,7 +282,7 @@ private:
     bool parse_invalid_braced_quantifier(); // Note: This function either parses and *fails*, or doesn't parse anything and returns false.
     Optional<u8> parse_legacy_octal_escape();
 
-    bool has_duplicate_in_current_alternative(ByteString const& name);
+    bool has_duplicate_in_current_alternative(DeprecatedFlyString const& name);
 
     size_t ensure_total_number_of_capturing_parenthesis();