Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -1514,8 +1514,8 @@
         "UIView",
     };
 
-    for (auto &Line : AnnotatedLines) {
-      for (FormatToken *FormatTok = Line->First; FormatTok;
+    auto CheckLineTokens = [&Keywords](const AnnotatedLine &Line) {
+      for (const FormatToken *FormatTok = Line.First; FormatTok;
            FormatTok = FormatTok->Next) {
         if ((FormatTok->Previous && FormatTok->Previous->is(tok::at) &&
              (FormatTok->isObjCAtKeyword(tok::objc_interface) ||
@@ -1536,6 +1536,15 @@
           return true;
         }
       }
+      return false;
+    };
+    for (auto Line : AnnotatedLines) {
+      if (CheckLineTokens(*Line))
+        return true;
+      for (auto ChildLine : Line->Children) {
+        if (CheckLineTokens(*ChildLine))
+          return true;
+      }
     }
     return false;
   }
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -12162,6 +12162,13 @@
       guessLanguage("foo.h", "int(^foo[(kNumEntries + 10)])(char, float);"));
 }
 
+TEST_F(FormatTest, GuessLanguageWithChildLines) {
+  EXPECT_EQ(FormatStyle::LK_Cpp,
+            guessLanguage("foo.h", "#define FOO ({ std::string s; })"));
+  EXPECT_EQ(FormatStyle::LK_ObjC,
+            guessLanguage("foo.h", "#define FOO ({ NSString *s; })"));
+}
+
 } // end namespace
 } // end namespace format
 } // end namespace clang