diff --git a/source/common/formatter/substitution_formatter.cc b/source/common/formatter/substitution_formatter.cc
index 1072ae132f6f..bd2dacc2f93a 100644
--- a/source/common/formatter/substitution_formatter.cc
+++ b/source/common/formatter/substitution_formatter.cc
@@ -300,6 +300,15 @@ std::vector<FormatterProviderPtr> SubstitutionFormatParser::parse(const std::str
         current_token = "";
       }
 
+      // escape '%%'
+      if (format.length() > pos+1) {
+        if (format[pos+1] == '%') {
+          current_token += '%';
+          pos++;
+          continue;
+        }
+      }
+
       std::smatch m;
       const std::string search_space = format.substr(pos);
       if (!std::regex_search(search_space, m, command_w_args_regex)) {
diff --git a/test/common/formatter/substitution_formatter_test.cc b/test/common/formatter/substitution_formatter_test.cc
index 1c3d9edd35b5..0a7ee48082a9 100644
--- a/test/common/formatter/substitution_formatter_test.cc
+++ b/test/common/formatter/substitution_formatter_test.cc
@@ -2405,8 +2405,7 @@ TEST(SubstitutionFormatterTest, ParserFailures) {
       "RESP(FIRST)%",
       "%REQ(valid)% %NOT_VALID%",
       "%REQ(FIRST?SECOND%",
-      "%%",
-      "%%HOSTNAME%PROTOCOL%",
+      "%HOSTNAME%PROTOCOL%",
       "%protocol%",
       "%REQ(TEST):%",
       "%REQ(TEST):3q4%",
@@ -2449,6 +2448,51 @@ TEST(SubstitutionFormatterTest, ParserSuccesses) {
   }
 }
 
+TEST(SubstitutionFormatterTest, EmptyFormatParse) {
+  Http::TestRequestHeaderMapImpl request_headers{{":method", "GET"}, {":path", "/"}};
+  Http::TestResponseHeaderMapImpl response_headers;
+  Http::TestResponseTrailerMapImpl response_trailers;
+  StreamInfo::MockStreamInfo stream_info;
+  std::string body;
+
+  auto providers = SubstitutionFormatParser::parse("");
+
+  EXPECT_EQ(providers.size(), 1);
+  EXPECT_EQ("", providers[0]->format(request_headers, response_headers, response_trailers,
+                                     stream_info, body));
+}
+
+TEST(SubstitutionFormatterTest, EscapingFormatParse) {
+  Http::TestRequestHeaderMapImpl request_headers{{":method", "GET"}, {":path", "/"}};
+  Http::TestResponseHeaderMapImpl response_headers;
+  Http::TestResponseTrailerMapImpl response_trailers;
+  StreamInfo::MockStreamInfo stream_info;
+  std::string body;
+
+  auto providers = SubstitutionFormatParser::parse("%%");
+
+  EXPECT_EQ(providers.size(), 1);
+  EXPECT_EQ("%", providers[0]->format(request_headers, response_headers, response_trailers,
+                                     stream_info, body));
+}
+
+TEST(SubstitutionFormatterTest, FormatterExtension) {
+  Http::TestRequestHeaderMapImpl request_headers{{":method", "GET"}, {":path", "/"}};
+  Http::TestResponseHeaderMapImpl response_headers;
+  Http::TestResponseTrailerMapImpl response_trailers;
+  StreamInfo::MockStreamInfo stream_info;
+  std::string body;
+
+  std::vector<CommandParserPtr> commands;
+  commands.push_back(std::make_unique<TestCommandParser>());
+
+  auto providers = SubstitutionFormatParser::parse("foo %COMMAND_EXTENSION(x)%", commands);
+
+  EXPECT_EQ(providers.size(), 2);
+  EXPECT_EQ("TestFormatter", providers[1]->format(request_headers, response_headers,
+                                                  response_trailers, stream_info, body));
+}
+
 } // namespace
 } // namespace Formatter
 } // namespace Envoy