Index: lib/Format/UnwrappedLineParser.cpp
===================================================================
--- lib/Format/UnwrappedLineParser.cpp
+++ lib/Format/UnwrappedLineParser.cpp
@@ -703,6 +703,13 @@
 // but only aims to correctly handle certain well known cases. It *must not*
 // return true in speculative cases.
 void UnwrappedLineParser::readTokenWithJavaScriptASI() {
+  bool PreviousIsAnnotation = false;
+  if (Line && Line->Tokens.size() > 1) {
+    // If the token before the previous one is an '@', the previous token is an
+    // annotation and can precede another identifier/value.
+    const FormatToken *PrePrevious = std::next(Line->Tokens.rend(), 2)->Tok;
+    PreviousIsAnnotation = PrePrevious->is(tok::at);
+  }
   FormatToken *Previous = FormatTok;
   readToken();
   FormatToken *Next = FormatTok;
@@ -714,7 +721,8 @@
   if (IsOnSameLine)
     return;
 
-  bool PreviousMustBeValue = mustBeJSIdentOrValue(Keywords, Previous);
+  bool PreviousMustBeValue =
+      !PreviousIsAnnotation && mustBeJSIdentOrValue(Keywords, Previous);
   if (Next->is(tok::exclaim) && PreviousMustBeValue)
     addUnwrappedLine();
   bool NextMustBeValue = mustBeJSIdentOrValue(Keywords, Next);
Index: unittests/Format/FormatTestJS.cpp
===================================================================
--- unittests/Format/FormatTestJS.cpp
+++ unittests/Format/FormatTestJS.cpp
@@ -686,6 +686,8 @@
   verifyFormat("x instanceof String", "x\n"
                                       "instanceof\n"
                                       "String");
+  verifyFormat("function f(@Foo bar) {}", "function f(@Foo\n"
+                                          "  bar) {}");
 }
 
 TEST_F(FormatTestJS, ClosureStyleCasts) {