Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -1570,8 +1570,10 @@
       const FormatToken *NextNonComment = Current->getNextNonComment();
       if (Current->is(TT_ConditionalExpr))
         return prec::Conditional;
-      if (NextNonComment && NextNonComment->is(tok::colon) &&
-          NextNonComment->is(TT_DictLiteral))
+      if (NextNonComment && Current->is(TT_SelectorName) &&
+          (NextNonComment->is(TT_DictLiteral) ||
+           (Style.Language == FormatStyle::LK_Proto &&
+            NextNonComment->is(tok::less))))
         return prec::Assignment;
       if (Current->is(TT_JsComputedPropertyName))
         return prec::Assignment;
Index: unittests/Format/FormatTestProto.cpp
===================================================================
--- unittests/Format/FormatTestProto.cpp
+++ unittests/Format/FormatTestProto.cpp
@@ -201,6 +201,12 @@
                "  field_c: \"OK\"\n"
                "  msg_field{field_d: 123}\n"
                "};");
+  verifyFormat("option (MyProto.options) = {\n"
+               "  field_a: OK\n"
+               "  field_b{field_c: OK}\n"
+               "  field_d: OKOKOK\n"
+               "  field_e: OK\n"
+               "}");
 
   // Support syntax with <> instead of {}.
   verifyFormat("option (MyProto.options) = {\n"
@@ -208,6 +214,13 @@
                "  msg_field: <field_d: 123>\n"
                "};");
 
+  verifyFormat("option (MyProto.options) = {\n"
+               "  field_a: OK\n"
+               "  field_b<field_c: OK>\n"
+               "  field_d: OKOKOK\n"
+               "  field_e: OK\n"
+               "}");
+
   verifyFormat("option (MyProto.options) = {\n"
                "  msg_field: <>\n"
                "  field_c: \"OK\",\n"