diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -1650,9 +1650,9 @@
                 : Current.Previous->is(tok::identifier);
         if (IsIdentifier ||
             Current.Previous->isOneOf(
-                tok::kw_namespace, tok::r_paren, tok::r_square, tok::r_brace,
-                tok::kw_false, tok::kw_true, Keywords.kw_type, Keywords.kw_get,
-                Keywords.kw_init, Keywords.kw_set) ||
+                tok::kw_default, tok::kw_namespace, tok::r_paren, tok::r_square,
+                tok::r_brace, tok::kw_false, tok::kw_true, Keywords.kw_type,
+                Keywords.kw_get, Keywords.kw_init, Keywords.kw_set) ||
             Current.Previous->Tok.isLiteral()) {
           Current.setType(TT_NonNullAssertion);
           return;
diff --git a/clang/unittests/Format/FormatTestCSharp.cpp b/clang/unittests/Format/FormatTestCSharp.cpp
--- a/clang/unittests/Format/FormatTestCSharp.cpp
+++ b/clang/unittests/Format/FormatTestCSharp.cpp
@@ -1078,6 +1078,16 @@
                MicrosoftStyle);
 }
 
+TEST_F(FormatTestCSharp, DefaultLiteral) {
+  FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
+
+  verifyFormat(
+      "T[] InitializeArray<T>(int length, T initialValue = default) {}", Style);
+  verifyFormat("System.Numerics.Complex fillValue = default;", Style);
+  verifyFormat("int Value { get } = default;", Style);
+  verifyFormat("int Value { get } = default!;", Style);
+}
+
 TEST_F(FormatTestCSharp, CSharpSpaces) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
   Style.SpaceBeforeSquareBrackets = false;