diff --git a/internal/core/format.go b/internal/core/format.go
index 4470cfb2..dc89782d 100755
--- a/internal/core/format.go
+++ b/internal/core/format.go
@@ -105,6 +105,7 @@ var FormatByExtension = map[string][]string{
 	`\.(?:dita)$`:                                 {".dita", "markup"},
 	`\.(?:org)$`:                                  {".org", "markup"},
 	`\.(?:jl)$`:                                   {".jl", "code"},
+	`\.(?:proto)$`:                                {".c", "code"},
 }
 
 // FormatFromExt takes a file extension and returns its [normExt, format]
diff --git a/testdata/features/lint.feature b/testdata/features/lint.feature
index 1aa8a022..a89e9477 100755
--- a/testdata/features/lint.feature
+++ b/testdata/features/lint.feature
@@ -22,6 +22,15 @@ Feature: Lint
             test.jl:47:3:vale.Annotations:'XXX' left in text
             """
 
+    Scenario: Lint a proto file
+        When I lint "test.proto"
+        Then the output should contain exactly:
+            """
+            test.proto:13:6:vale.Annotations:'NOTE' left in text
+            test.proto:22:4:vale.Annotations:'XXX' left in text
+            test.proto:31:1:vale.Annotations:'NOTE' left in text
+            """
+
     Scenario: Lint an Org file
         When I lint "test.org"
         Then the output should contain exactly:
diff --git a/testdata/fixtures/formats/test.proto b/testdata/fixtures/formats/test.proto
new file mode 100755
index 00000000..8fe105f4
--- /dev/null
+++ b/testdata/fixtures/formats/test.proto
@@ -0,0 +1,41 @@
+syntax = "proto3";
+
+package foo.bar.v1;
+
+import "google/api/annotations.proto";
+
+option java_package = "com.company.foo.bar.v1";
+option java_outer_classname = "ApiProtoXXX";
+
+
+// The foo service
+service FooService {
+  // NOTE: this is a RPC comment
+  rpc GetBar(GetBarRequest) returns (GetBarResponse) {
+    option (google.api.http) = {
+      get: "/v1/{name=bars/*}"
+    };
+    option (google.api.method_signature) = "name";
+  }
+}
+
+/* XXX: this is also a comment */
+message GetBarRequest {
+    // Note: Field comment inside a message.
+    string name = 1;
+}
+
+/*
+Comment.
+
+NOTE: I am a multilinek comment, so I span
+over multiple lines
+*/
+message GetBarResponse {
+    string todo = 1;
+}
+
+// The following should not get matched
+message XXX {
+
+}