diff --git a/Tests/LibRegex/Regex.cpp b/Tests/LibRegex/Regex.cpp
index 0193ce1b46a..c9bb6e16226 100644
--- a/Tests/LibRegex/Regex.cpp
+++ b/Tests/LibRegex/Regex.cpp
@@ -682,6 +682,7 @@ TEST_CASE(ECMA262_match)
         { "[\\0]"sv, "\0"sv, true, combine_flags(ECMAScriptFlags::Unicode, ECMAScriptFlags::BrowserExtended) },
         { "[\\01]"sv, "\1"sv, true, ECMAScriptFlags::BrowserExtended },
         { "(\0|a)"sv, "a"sv, true }, // #9686, Should allow null bytes in pattern
+        { "(.*?)a(?!(a+)b\\2c)\\2(.*)"sv, "baaabaac"sv, true }, // #6042, Groups inside lookarounds may be referenced outside, but their contents appear empty if the pattern in the lookaround fails.
         { "a|$"sv, "x"sv, true, (ECMAScriptFlags)regex::AllFlags::Global }, // #11940, Global (not the 'g' flag) regexps should attempt to match the zero-length end of the string too.
     };
     // clang-format on
diff --git a/Userland/Libraries/LibRegex/RegexByteCode.cpp b/Userland/Libraries/LibRegex/RegexByteCode.cpp
index 6177a1f3e2f..050f067ae00 100644
--- a/Userland/Libraries/LibRegex/RegexByteCode.cpp
+++ b/Userland/Libraries/LibRegex/RegexByteCode.cpp
@@ -329,8 +329,11 @@ ALWAYS_INLINE ExecutionResult OpCode_ClearCaptureGroup::execute(MatchInput const
 {
     if (input.match_index < state.capture_group_matches.size()) {
         auto& group = state.capture_group_matches[input.match_index];
-        if (id() < group.size())
-            group[id()].reset();
+        auto group_id = id();
+        if (group_id >= group.size())
+            group.resize(group_id + 1);
+
+        group[group_id].reset();
     }
     return ExecutionResult::Continue;
 }