Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -2516,7 +2516,9 @@
       return true;
     if (Left.is(tok::l_brace) && Line.Level == 0 &&
         (Line.startsWith(tok::kw_enum) ||
-         Line.startsWith(tok::kw_export, tok::kw_enum)))
+         Line.startsWith(tok::kw_const, tok::kw_enum) ||
+         Line.startsWith(tok::kw_export, tok::kw_enum) ||
+         Line.startsWith(tok::kw_export, tok::kw_const, tok::kw_enum)))
       // JavaScript top-level enum key/value pairs are put on separate lines
       // instead of bin-packing.
       return true;
Index: unittests/Format/FormatTestJS.cpp
===================================================================
--- unittests/Format/FormatTestJS.cpp
+++ unittests/Format/FormatTestJS.cpp
@@ -1414,6 +1414,14 @@
                "  B\n"
                "}\n"
                "var x = 1;");
+  verifyFormat("const enum Foo {\n"
+               "  A = 1,\n"
+               "  B\n"
+               "}");
+  verifyFormat("export const enum Foo {\n"
+               "  A = 1,\n"
+               "  B\n"
+               "}");
 }
 
 TEST_F(FormatTestJS, MetadataAnnotations) {