--- a/src/google/protobuf/compiler/parser.cc	(index)
+++ b/src/google/protobuf/compiler/parser.cc	(working tree)
@@ -670,11 +670,6 @@ bool Parser::Parse(io::Tokenizer* input, FileDescriptorProto* file) {
         file->set_syntax(syntax_identifier_);
       }
     } else if (!stop_after_syntax_identifier_) {
-      ABSL_LOG(WARNING) << "No syntax specified for the proto file: "
-                        << file->name()
-                        << ". Please use 'syntax = \"proto2\";' "
-                        << "or 'syntax = \"proto3\";' to specify a syntax "
-                        << "version. (Defaulted to proto2 syntax.)";
       syntax_identifier_ = "proto2";
     }