diff --git a/Documentation/Evolution/RegexSyntax.md b/Documentation/Evolution/RegexSyntax.md
index 9f4c6e8a0..97e3b45da 100644
--- a/Documentation/Evolution/RegexSyntax.md
+++ b/Documentation/Evolution/RegexSyntax.md
@@ -263,7 +263,7 @@ UnicodeScalar -> '\u{' HexDigit{1...} '}'
                | '\o{' OctalDigit{1...} '}'
                | '\0' OctalDigit{0...3}
 
-HexDigit   -> [0-9a-zA-Z]
+HexDigit   -> [0-9a-fA-F]
 OctalDigit -> [0-7]
 
 NamedScalar -> '\N{' ScalarName '}'
diff --git a/Tests/RegexTests/ParseTests.swift b/Tests/RegexTests/ParseTests.swift
index c6ff3e46d..5e3defb11 100644
--- a/Tests/RegexTests/ParseTests.swift
+++ b/Tests/RegexTests/ParseTests.swift
@@ -2313,6 +2313,10 @@ extension RegexTests {
     diagnosticTest("{5}", .quantifierRequiresOperand("{5}"))
     diagnosticTest("{1,3}", .quantifierRequiresOperand("{1,3}"))
 
+    // MARK: Unicode scalars
+
+    diagnosticTest(#"\u{G}"#, .expectedNumber("G", kind: .hex))
+
     // MARK: Matching options
 
     diagnosticTest(#"(?^-"#, .cannotRemoveMatchingOptionsAfterCaret)