Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -506,7 +506,8 @@
       if (Line.MustBeDeclaration && Contexts.size() == 1 &&
           !Contexts.back().IsExpression && !Line.startsWith(TT_ObjCProperty) &&
           (!Tok->Previous ||
-           !Tok->Previous->isOneOf(tok::kw_decltype, TT_LeadingJavaAnnotation)))
+           !Tok->Previous->isOneOf(tok::kw_decltype, tok::kw___attribute,
+                                   TT_LeadingJavaAnnotation)))
         Line.MightBeFunctionDecl = true;
       break;
     case tok::l_square:
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -5554,6 +5554,11 @@
   verifyFormat("SomeType s __attribute__((unused)) (InitValue);");
   verifyFormat("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa __attribute__((unused))\n"
                "aaaaaaaaaaaaaaaaaaaaaaa(int i);");
+  FormatStyle AfterType = getLLVMStyle();
+  AfterType.AlwaysBreakAfterDefinitionReturnType = FormatStyle::DRTBS_All;
+  verifyFormat("__attribute__((nodebug)) void\n"
+               "foo() {}\n",
+               AfterType);
 }
 
 TEST_F(FormatTest, UnderstandsEllipsis) {