diff --git a/Tests/LibUnicode/TestUnicodeCharacterTypes.cpp b/Tests/LibUnicode/TestUnicodeCharacterTypes.cpp
index dfc9c5fae62..d6eb43e103e 100644
--- a/Tests/LibUnicode/TestUnicodeCharacterTypes.cpp
+++ b/Tests/LibUnicode/TestUnicodeCharacterTypes.cpp
@@ -53,306 +53,306 @@ TEST_CASE(to_unicode_uppercase)
 TEST_CASE(to_unicode_lowercase_unconditional_special_casing)
 {
     // LATIN SMALL LETTER SHARP S
-    auto result = Unicode::to_unicode_lowercase_full("\u00DF"sv);
+    auto result = MUST(Unicode::to_unicode_lowercase_full("\u00DF"sv));
     EXPECT_EQ(result, "\u00DF");
 
     // LATIN CAPITAL LETTER I WITH DOT ABOVE
-    result = Unicode::to_unicode_lowercase_full("\u0130"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u0130"sv));
     EXPECT_EQ(result, "\u0069\u0307");
 
     // LATIN SMALL LIGATURE FF
-    result = Unicode::to_unicode_lowercase_full("\uFB00"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\uFB00"sv));
     EXPECT_EQ(result, "\uFB00");
 
     // LATIN SMALL LIGATURE FI
-    result = Unicode::to_unicode_lowercase_full("\uFB01"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\uFB01"sv));
     EXPECT_EQ(result, "\uFB01");
 
     // LATIN SMALL LIGATURE FL
-    result = Unicode::to_unicode_lowercase_full("\uFB02"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\uFB02"sv));
     EXPECT_EQ(result, "\uFB02");
 
     // LATIN SMALL LIGATURE FFI
-    result = Unicode::to_unicode_lowercase_full("\uFB03"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\uFB03"sv));
     EXPECT_EQ(result, "\uFB03");
 
     // LATIN SMALL LIGATURE FFL
-    result = Unicode::to_unicode_lowercase_full("\uFB04"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\uFB04"sv));
     EXPECT_EQ(result, "\uFB04");
 
     // LATIN SMALL LIGATURE LONG S T
-    result = Unicode::to_unicode_lowercase_full("\uFB05"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\uFB05"sv));
     EXPECT_EQ(result, "\uFB05");
 
     // LATIN SMALL LIGATURE ST
-    result = Unicode::to_unicode_lowercase_full("\uFB06"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\uFB06"sv));
     EXPECT_EQ(result, "\uFB06");
 
     // GREEK SMALL LETTER ALPHA WITH PERISPOMENI AND YPOGEGRAMMENI
-    result = Unicode::to_unicode_lowercase_full("\u1FB7"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u1FB7"sv));
     EXPECT_EQ(result, "\u1FB7");
 
     // GREEK SMALL LETTER ETA WITH PERISPOMENI AND YPOGEGRAMMENI
-    result = Unicode::to_unicode_lowercase_full("\u1FC7"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u1FC7"sv));
     EXPECT_EQ(result, "\u1FC7");
 
     // GREEK SMALL LETTER OMEGA WITH PERISPOMENI AND YPOGEGRAMMENI
-    result = Unicode::to_unicode_lowercase_full("\u1FF7"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u1FF7"sv));
     EXPECT_EQ(result, "\u1FF7");
 }
 
 TEST_CASE(to_unicode_lowercase_special_casing_sigma)
 {
-    auto result = Unicode::to_unicode_lowercase_full("ABCI"sv);
+    auto result = MUST(Unicode::to_unicode_lowercase_full("ABCI"sv));
     EXPECT_EQ(result, "abci");
 
     // Sigma preceded by A
-    result = Unicode::to_unicode_lowercase_full("A\u03A3"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("A\u03A3"sv));
     EXPECT_EQ(result, "a\u03C2");
 
     // Sigma preceded by FEMININE ORDINAL INDICATOR
-    result = Unicode::to_unicode_lowercase_full("\u00AA\u03A3"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u00AA\u03A3"sv));
     EXPECT_EQ(result, "\u00AA\u03C2");
 
     // Sigma preceded by ROMAN NUMERAL ONE
-    result = Unicode::to_unicode_lowercase_full("\u2160\u03A3"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u2160\u03A3"sv));
     EXPECT_EQ(result, "\u2170\u03C2");
 
     // Sigma preceded by COMBINING GREEK YPOGEGRAMMENI
-    result = Unicode::to_unicode_lowercase_full("\u0345\u03A3"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u0345\u03A3"sv));
     EXPECT_EQ(result, "\u0345\u03C3");
 
     // Sigma preceded by A and FULL STOP
-    result = Unicode::to_unicode_lowercase_full("A.\u03A3"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("A.\u03A3"sv));
     EXPECT_EQ(result, "a.\u03C2");
 
     // Sigma preceded by A and MONGOLIAN VOWEL SEPARATOR
-    result = Unicode::to_unicode_lowercase_full("A\u180E\u03A3"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("A\u180E\u03A3"sv));
     EXPECT_EQ(result, "a\u180E\u03C2");
 
     // Sigma preceded by A and MONGOLIAN VOWEL SEPARATOR, followed by B
-    result = Unicode::to_unicode_lowercase_full("A\u180E\u03A3B"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("A\u180E\u03A3B"sv));
     EXPECT_EQ(result, "a\u180E\u03C3b");
 
     // Sigma followed by A
-    result = Unicode::to_unicode_lowercase_full("\u03A3A"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u03A3A"sv));
     EXPECT_EQ(result, "\u03C3a");
 
     // Sigma preceded by A, followed by MONGOLIAN VOWEL SEPARATOR
-    result = Unicode::to_unicode_lowercase_full("A\u03A3\u180E"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("A\u03A3\u180E"sv));
     EXPECT_EQ(result, "a\u03C2\u180E");
 
     // Sigma preceded by A, followed by MONGOLIAN VOWEL SEPARATOR and B
-    result = Unicode::to_unicode_lowercase_full("A\u03A3\u180EB"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("A\u03A3\u180EB"sv));
     EXPECT_EQ(result, "a\u03C3\u180Eb");
 
     // Sigma preceded by A and MONGOLIAN VOWEL SEPARATOR, followed by MONGOLIAN VOWEL SEPARATOR
-    result = Unicode::to_unicode_lowercase_full("A\u180E\u03A3\u180E"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("A\u180E\u03A3\u180E"sv));
     EXPECT_EQ(result, "a\u180E\u03C2\u180E");
 
     // Sigma preceded by A and MONGOLIAN VOWEL SEPARATOR, followed by MONGOLIAN VOWEL SEPARATOR and B
-    result = Unicode::to_unicode_lowercase_full("A\u180E\u03A3\u180EB"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("A\u180E\u03A3\u180EB"sv));
     EXPECT_EQ(result, "a\u180E\u03C3\u180Eb");
 }
 
 TEST_CASE(to_unicode_lowercase_special_casing_i)
 {
     // LATIN CAPITAL LETTER I
-    auto result = Unicode::to_unicode_lowercase_full("I"sv, "en"sv);
+    auto result = MUST(Unicode::to_unicode_lowercase_full("I"sv, "en"sv));
     EXPECT_EQ(result, "i"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I"sv, "az"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I"sv, "az"sv));
     EXPECT_EQ(result, "\u0131"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I"sv, "tr"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I"sv, "tr"sv));
     EXPECT_EQ(result, "\u0131"sv);
 
     // LATIN CAPITAL LETTER I WITH DOT ABOVE
-    result = Unicode::to_unicode_lowercase_full("\u0130"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u0130"sv, "en"sv));
     EXPECT_EQ(result, "\u0069\u0307"sv);
 
-    result = Unicode::to_unicode_lowercase_full("\u0130"sv, "az"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u0130"sv, "az"sv));
     EXPECT_EQ(result, "i"sv);
 
-    result = Unicode::to_unicode_lowercase_full("\u0130"sv, "tr"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u0130"sv, "tr"sv));
     EXPECT_EQ(result, "i"sv);
 
     // LATIN CAPITAL LETTER I followed by COMBINING DOT ABOVE
-    result = Unicode::to_unicode_lowercase_full("I\u0307"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I\u0307"sv, "en"sv));
     EXPECT_EQ(result, "i\u0307"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I\u0307"sv, "az"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I\u0307"sv, "az"sv));
     EXPECT_EQ(result, "i"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I\u0307"sv, "tr"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I\u0307"sv, "tr"sv));
     EXPECT_EQ(result, "i"sv);
 
     // LATIN CAPITAL LETTER I followed by combining class 0 and COMBINING DOT ABOVE
-    result = Unicode::to_unicode_lowercase_full("IA\u0307"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("IA\u0307"sv, "en"sv));
     EXPECT_EQ(result, "ia\u0307"sv);
 
-    result = Unicode::to_unicode_lowercase_full("IA\u0307"sv, "az"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("IA\u0307"sv, "az"sv));
     EXPECT_EQ(result, "\u0131a\u0307"sv);
 
-    result = Unicode::to_unicode_lowercase_full("IA\u0307"sv, "tr"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("IA\u0307"sv, "tr"sv));
     EXPECT_EQ(result, "\u0131a\u0307"sv);
 }
 
 TEST_CASE(to_unicode_lowercase_special_casing_more_above)
 {
     // LATIN CAPITAL LETTER I
-    auto result = Unicode::to_unicode_lowercase_full("I"sv, "en"sv);
+    auto result = MUST(Unicode::to_unicode_lowercase_full("I"sv, "en"sv));
     EXPECT_EQ(result, "i"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I"sv, "lt"sv));
     EXPECT_EQ(result, "i"sv);
 
     // LATIN CAPITAL LETTER J
-    result = Unicode::to_unicode_lowercase_full("J"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("J"sv, "en"sv));
     EXPECT_EQ(result, "j"sv);
 
-    result = Unicode::to_unicode_lowercase_full("J"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("J"sv, "lt"sv));
     EXPECT_EQ(result, "j"sv);
 
     // LATIN CAPITAL LETTER I WITH OGONEK
-    result = Unicode::to_unicode_lowercase_full("\u012e"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u012e"sv, "en"sv));
     EXPECT_EQ(result, "\u012f"sv);
 
-    result = Unicode::to_unicode_lowercase_full("\u012e"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u012e"sv, "lt"sv));
     EXPECT_EQ(result, "\u012f"sv);
 
     // LATIN CAPITAL LETTER I followed by COMBINING GRAVE ACCENT
-    result = Unicode::to_unicode_lowercase_full("I\u0300"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I\u0300"sv, "en"sv));
     EXPECT_EQ(result, "i\u0300"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I\u0300"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I\u0300"sv, "lt"sv));
     EXPECT_EQ(result, "i\u0307\u0300"sv);
 
     // LATIN CAPITAL LETTER J followed by COMBINING GRAVE ACCENT
-    result = Unicode::to_unicode_lowercase_full("J\u0300"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("J\u0300"sv, "en"sv));
     EXPECT_EQ(result, "j\u0300"sv);
 
-    result = Unicode::to_unicode_lowercase_full("J\u0300"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("J\u0300"sv, "lt"sv));
     EXPECT_EQ(result, "j\u0307\u0300"sv);
 
     // LATIN CAPITAL LETTER I WITH OGONEK followed by COMBINING GRAVE ACCENT
-    result = Unicode::to_unicode_lowercase_full("\u012e\u0300"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u012e\u0300"sv, "en"sv));
     EXPECT_EQ(result, "\u012f\u0300"sv);
 
-    result = Unicode::to_unicode_lowercase_full("\u012e\u0300"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("\u012e\u0300"sv, "lt"sv));
     EXPECT_EQ(result, "\u012f\u0307\u0300"sv);
 }
 
 TEST_CASE(to_unicode_lowercase_special_casing_not_before_dot)
 {
     // LATIN CAPITAL LETTER I
-    auto result = Unicode::to_unicode_lowercase_full("I"sv, "en"sv);
+    auto result = MUST(Unicode::to_unicode_lowercase_full("I"sv, "en"sv));
     EXPECT_EQ(result, "i"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I"sv, "az"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I"sv, "az"sv));
     EXPECT_EQ(result, "\u0131"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I"sv, "tr"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I"sv, "tr"sv));
     EXPECT_EQ(result, "\u0131"sv);
 
     // LATIN CAPITAL LETTER I followed by COMBINING DOT ABOVE
-    result = Unicode::to_unicode_lowercase_full("I\u0307"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I\u0307"sv, "en"sv));
     EXPECT_EQ(result, "i\u0307"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I\u0307"sv, "az"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I\u0307"sv, "az"sv));
     EXPECT_EQ(result, "i"sv);
 
-    result = Unicode::to_unicode_lowercase_full("I\u0307"sv, "tr"sv);
+    result = MUST(Unicode::to_unicode_lowercase_full("I\u0307"sv, "tr"sv));
     EXPECT_EQ(result, "i"sv);
 }
 
 TEST_CASE(to_unicode_uppercase_unconditional_special_casing)
 {
     // LATIN SMALL LETTER SHARP S
-    auto result = Unicode::to_unicode_uppercase_full("\u00DF"sv);
+    auto result = MUST(Unicode::to_unicode_uppercase_full("\u00DF"sv));
     EXPECT_EQ(result, "\u0053\u0053");
 
     // LATIN CAPITAL LETTER I WITH DOT ABOVE
-    result = Unicode::to_unicode_uppercase_full("\u0130"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\u0130"sv));
     EXPECT_EQ(result, "\u0130");
 
     // LATIN SMALL LIGATURE FF
-    result = Unicode::to_unicode_uppercase_full("\uFB00"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\uFB00"sv));
     EXPECT_EQ(result, "\u0046\u0046");
 
     // LATIN SMALL LIGATURE FI
-    result = Unicode::to_unicode_uppercase_full("\uFB01"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\uFB01"sv));
     EXPECT_EQ(result, "\u0046\u0049");
 
     // LATIN SMALL LIGATURE FL
-    result = Unicode::to_unicode_uppercase_full("\uFB02"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\uFB02"sv));
     EXPECT_EQ(result, "\u0046\u004C");
 
     // LATIN SMALL LIGATURE FFI
-    result = Unicode::to_unicode_uppercase_full("\uFB03"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\uFB03"sv));
     EXPECT_EQ(result, "\u0046\u0046\u0049");
 
     // LATIN SMALL LIGATURE FFL
-    result = Unicode::to_unicode_uppercase_full("\uFB04"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\uFB04"sv));
     EXPECT_EQ(result, "\u0046\u0046\u004C");
 
     // LATIN SMALL LIGATURE LONG S T
-    result = Unicode::to_unicode_uppercase_full("\uFB05"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\uFB05"sv));
     EXPECT_EQ(result, "\u0053\u0054");
 
     // LATIN SMALL LIGATURE ST
-    result = Unicode::to_unicode_uppercase_full("\uFB06"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\uFB06"sv));
     EXPECT_EQ(result, "\u0053\u0054");
 
     // GREEK SMALL LETTER IOTA WITH DIALYTIKA AND TONOS
-    result = Unicode::to_unicode_uppercase_full("\u0390"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\u0390"sv));
     EXPECT_EQ(result, "\u0399\u0308\u0301");
 
     // GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND TONOS
-    result = Unicode::to_unicode_uppercase_full("\u03B0"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\u03B0"sv));
     EXPECT_EQ(result, "\u03A5\u0308\u0301");
 
     // GREEK SMALL LETTER ALPHA WITH PERISPOMENI AND YPOGEGRAMMENI
-    result = Unicode::to_unicode_uppercase_full("\u1FB7"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\u1FB7"sv));
     EXPECT_EQ(result, "\u0391\u0342\u0399");
 
     // GREEK SMALL LETTER ETA WITH PERISPOMENI AND YPOGEGRAMMENI
-    result = Unicode::to_unicode_uppercase_full("\u1FC7"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\u1FC7"sv));
     EXPECT_EQ(result, "\u0397\u0342\u0399");
 
     // GREEK SMALL LETTER OMEGA WITH PERISPOMENI AND YPOGEGRAMMENI
-    result = Unicode::to_unicode_uppercase_full("\u1FF7"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("\u1FF7"sv));
     EXPECT_EQ(result, "\u03A9\u0342\u0399");
 }
 
 TEST_CASE(to_unicode_uppercase_special_casing_soft_dotted)
 {
     // LATIN SMALL LETTER I
-    auto result = Unicode::to_unicode_uppercase_full("i"sv, "en"sv);
+    auto result = MUST(Unicode::to_unicode_uppercase_full("i"sv, "en"sv));
     EXPECT_EQ(result, "I"sv);
 
-    result = Unicode::to_unicode_uppercase_full("i"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("i"sv, "lt"sv));
     EXPECT_EQ(result, "I"sv);
 
     // LATIN SMALL LETTER J
-    result = Unicode::to_unicode_uppercase_full("j"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("j"sv, "en"sv));
     EXPECT_EQ(result, "J"sv);
 
-    result = Unicode::to_unicode_uppercase_full("j"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("j"sv, "lt"sv));
     EXPECT_EQ(result, "J"sv);
 
     // LATIN SMALL LETTER I followed by COMBINING DOT ABOVE
-    result = Unicode::to_unicode_uppercase_full("i\u0307"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("i\u0307"sv, "en"sv));
     EXPECT_EQ(result, "I\u0307"sv);
 
-    result = Unicode::to_unicode_uppercase_full("i\u0307"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("i\u0307"sv, "lt"sv));
     EXPECT_EQ(result, "I"sv);
 
     // LATIN SMALL LETTER J followed by COMBINING DOT ABOVE
-    result = Unicode::to_unicode_uppercase_full("j\u0307"sv, "en"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("j\u0307"sv, "en"sv));
     EXPECT_EQ(result, "J\u0307"sv);
 
-    result = Unicode::to_unicode_uppercase_full("j\u0307"sv, "lt"sv);
+    result = MUST(Unicode::to_unicode_uppercase_full("j\u0307"sv, "lt"sv));
     EXPECT_EQ(result, "J"sv);
 }
 
diff --git a/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp b/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
index cbab96db61a..e0abc3aa5de 100644
--- a/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
+++ b/Userland/Libraries/LibJS/Runtime/StringPrototype.cpp
@@ -916,13 +916,13 @@ static ThrowCompletionOr<DeprecatedString> transform_case(VM& vm, StringView str
     // 9. If targetCase is lower, then
     case TargetCase::Lower:
         // a. Let newCodePoints be a List whose elements are the result of a lowercase transformation of codePoints according to an implementation-derived algorithm using locale or the Unicode Default Case Conversion algorithm.
-        new_code_points = Unicode::to_unicode_lowercase_full(string, *locale);
+        new_code_points = TRY_OR_THROW_OOM(vm, Unicode::to_unicode_lowercase_full(string, *locale));
         break;
     // 10. Else,
     case TargetCase::Upper:
         // a. Assert: targetCase is upper.
         // b. Let newCodePoints be a List whose elements are the result of an uppercase transformation of codePoints according to an implementation-derived algorithm using locale or the Unicode Default Case Conversion algorithm.
-        new_code_points = Unicode::to_unicode_uppercase_full(string, *locale);
+        new_code_points = TRY_OR_THROW_OOM(vm, Unicode::to_unicode_uppercase_full(string, *locale));
         break;
     default:
         VERIFY_NOT_REACHED();
@@ -964,7 +964,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::to_locale_uppercase)
 JS_DEFINE_NATIVE_FUNCTION(StringPrototype::to_lowercase)
 {
     auto string = TRY(ak_string_from(vm));
-    auto lowercase = Unicode::to_unicode_lowercase_full(string);
+    auto lowercase = TRY_OR_THROW_OOM(vm, Unicode::to_unicode_lowercase_full(string));
     return PrimitiveString::create(vm, move(lowercase));
 }
 
@@ -978,7 +978,7 @@ JS_DEFINE_NATIVE_FUNCTION(StringPrototype::to_string)
 JS_DEFINE_NATIVE_FUNCTION(StringPrototype::to_uppercase)
 {
     auto string = TRY(ak_string_from(vm));
-    auto uppercase = Unicode::to_unicode_uppercase_full(string);
+    auto uppercase = TRY_OR_THROW_OOM(vm, Unicode::to_unicode_uppercase_full(string));
     return PrimitiveString::create(vm, move(uppercase));
 }
 
diff --git a/Userland/Libraries/LibUnicode/CharacterTypes.cpp b/Userland/Libraries/LibUnicode/CharacterTypes.cpp
index 658983f8ca6..fb7bd919a55 100644
--- a/Userland/Libraries/LibUnicode/CharacterTypes.cpp
+++ b/Userland/Libraries/LibUnicode/CharacterTypes.cpp
@@ -221,7 +221,7 @@ u32 __attribute__((weak)) to_unicode_uppercase(u32 code_point)
     return to_ascii_uppercase(code_point);
 }
 
-DeprecatedString to_unicode_lowercase_full(StringView string, [[maybe_unused]] Optional<StringView> locale)
+ErrorOr<DeprecatedString> to_unicode_lowercase_full(StringView string, [[maybe_unused]] Optional<StringView> locale)
 {
 #if ENABLE_UNICODE_DATA
     Utf8View view { string };
@@ -236,12 +236,12 @@ DeprecatedString to_unicode_lowercase_full(StringView string, [[maybe_unused]] O
 
         auto const* special_casing = find_matching_special_case(code_point, view, locale, index, byte_length);
         if (!special_casing) {
-            builder.append_code_point(to_unicode_lowercase(code_point));
+            TRY(builder.try_append_code_point(to_unicode_lowercase(code_point)));
             continue;
         }
 
         for (size_t i = 0; i < special_casing->lowercase_mapping_size; ++i)
-            builder.append_code_point(special_casing->lowercase_mapping[i]);
+            TRY(builder.try_append_code_point(special_casing->lowercase_mapping[i]));
     }
 
     return builder.build();
@@ -250,7 +250,7 @@ DeprecatedString to_unicode_lowercase_full(StringView string, [[maybe_unused]] O
 #endif
 }
 
-DeprecatedString to_unicode_uppercase_full(StringView string, [[maybe_unused]] Optional<StringView> locale)
+ErrorOr<DeprecatedString> to_unicode_uppercase_full(StringView string, [[maybe_unused]] Optional<StringView> locale)
 {
 #if ENABLE_UNICODE_DATA
     Utf8View view { string };
@@ -265,12 +265,12 @@ DeprecatedString to_unicode_uppercase_full(StringView string, [[maybe_unused]] O
 
         auto const* special_casing = find_matching_special_case(code_point, view, locale, index, byte_length);
         if (!special_casing) {
-            builder.append_code_point(to_unicode_uppercase(code_point));
+            TRY(builder.try_append_code_point(to_unicode_uppercase(code_point)));
             continue;
         }
 
         for (size_t i = 0; i < special_casing->uppercase_mapping_size; ++i)
-            builder.append_code_point(special_casing->uppercase_mapping[i]);
+            TRY(builder.try_append_code_point(special_casing->uppercase_mapping[i]));
     }
 
     return builder.build();
diff --git a/Userland/Libraries/LibUnicode/CharacterTypes.h b/Userland/Libraries/LibUnicode/CharacterTypes.h
index e3b7ab0af69..25d48ff889c 100644
--- a/Userland/Libraries/LibUnicode/CharacterTypes.h
+++ b/Userland/Libraries/LibUnicode/CharacterTypes.h
@@ -39,8 +39,8 @@ Span<SpecialCasing const* const> special_case_mapping(u32 code_point);
 u32 to_unicode_lowercase(u32 code_point);
 u32 to_unicode_uppercase(u32 code_point);
 
-DeprecatedString to_unicode_lowercase_full(StringView, Optional<StringView> locale = {});
-DeprecatedString to_unicode_uppercase_full(StringView, Optional<StringView> locale = {});
+ErrorOr<DeprecatedString> to_unicode_lowercase_full(StringView, Optional<StringView> locale = {});
+ErrorOr<DeprecatedString> to_unicode_uppercase_full(StringView, Optional<StringView> locale = {});
 
 Optional<GeneralCategory> general_category_from_string(StringView);
 bool code_point_has_general_category(u32 code_point, GeneralCategory general_category);
diff --git a/Userland/Libraries/LibWeb/Layout/TextNode.cpp b/Userland/Libraries/LibWeb/Layout/TextNode.cpp
index 3d0512fd907..cb866d021ae 100644
--- a/Userland/Libraries/LibWeb/Layout/TextNode.cpp
+++ b/Userland/Libraries/LibWeb/Layout/TextNode.cpp
@@ -32,7 +32,7 @@ static bool is_all_whitespace(StringView string)
     return true;
 }
 
-static DeprecatedString apply_text_transform(DeprecatedString const& string, CSS::TextTransform text_transform)
+static ErrorOr<DeprecatedString> apply_text_transform(DeprecatedString const& string, CSS::TextTransform text_transform)
 {
     if (text_transform == CSS::TextTransform::Uppercase)
         return Unicode::to_unicode_uppercase_full(string);
@@ -44,7 +44,7 @@ static DeprecatedString apply_text_transform(DeprecatedString const& string, CSS
 // NOTE: This collapses whitespace into a single ASCII space if collapse is true.
 void TextNode::compute_text_for_rendering(bool collapse)
 {
-    auto data = apply_text_transform(dom_node().data(), computed_values().text_transform());
+    auto data = apply_text_transform(dom_node().data(), computed_values().text_transform()).release_value_but_fixme_should_propagate_errors();
 
     if (dom_node().is_password_input()) {
         m_text_for_rendering = DeprecatedString::repeated('*', data.length());