Index: clang/lib/Format/Format.cpp
===================================================================
--- clang/lib/Format/Format.cpp
+++ clang/lib/Format/Format.cpp
@@ -640,6 +640,7 @@
     Expanded.BraceWrapping.AfterNamespace = true;
     Expanded.BraceWrapping.AfterObjCDeclaration = true;
     Expanded.BraceWrapping.AfterStruct = true;
+    Expanded.BraceWrapping.AfterUnion = true;
     Expanded.BraceWrapping.AfterExternBlock = true;
     Expanded.BraceWrapping.BeforeCatch = true;
     Expanded.BraceWrapping.BeforeElse = true;
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -11086,6 +11086,9 @@
                "{\n"
                "  int x;\n"
                "};\n"
+               "union C\n"
+               "{\n"
+               "};\n"
                "} // namespace a",
                AllmanBraceStyle);