Index: clang/lib/Format/UnwrappedLineFormatter.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineFormatter.cpp
+++ clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -643,6 +643,7 @@
     unsigned Length = 0;
     bool EndsWithComment = false;
     bool InPPDirective = I[0]->InPPDirective;
+    bool InMacroBody = I[0]->InMacroBody;
     const unsigned Level = I[0]->Level;
     for (; NumStmts < 3; ++NumStmts) {
       if (I + 1 + NumStmts == E)
@@ -650,6 +651,8 @@
       const AnnotatedLine *Line = I[1 + NumStmts];
       if (Line->InPPDirective != InPPDirective)
         break;
+      if(Line->InMacroBody != InMacroBody)
+        break;
       if (Line->First->isOneOf(tok::kw_case, tok::kw_default, tok::r_brace))
         break;
       if (Line->First->isOneOf(tok::kw_if, tok::kw_for, tok::kw_switch,
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -2999,6 +2999,10 @@
                "}",
                Style);
   Style.ColumnLimit = 21;
+  verifyFormat("#define X           \\\n"
+               "  case 0: break;\n"
+               "#include \"f\"",
+               Style);
   verifyFormat("switch (a) {\n"
                "case 1: x = 1; break;\n"
                "case 2: return;\n"