diff --git a/benchmark/package.json b/benchmark/package.json
index 1b148c327b..f162e068bb 100644
--- a/benchmark/package.json
+++ b/benchmark/package.json
@@ -72,6 +72,6 @@
     "suppress-warnings": "^1.0.2",
     "tstl": "^3.0.0",
     "uuid": "^9.0.1",
-    "typia": "../typia-6.10.4-dev.20240925.tgz"
+    "typia": "../typia-6.11.1.tgz"
   }
 }
\ No newline at end of file
diff --git a/debug/package.json b/debug/package.json
index 31bf134b56..51198ef52c 100644
--- a/debug/package.json
+++ b/debug/package.json
@@ -17,7 +17,7 @@
   },
   "dependencies": {
     "tstl": "^3.0.0",
-    "typia": "../typia-6.11.0.tgz",
+    "typia": "../typia-6.11.1.tgz",
     "uuid": "^10.0.0"
   }
 }
\ No newline at end of file
diff --git a/debug/src/protobuf.ts b/debug/src/protobuf.ts
new file mode 100644
index 0000000000..e65cb56800
--- /dev/null
+++ b/debug/src/protobuf.ts
@@ -0,0 +1,12 @@
+import typia from "typia";
+
+interface MyObj {
+  private: boolean | null;
+}
+
+const encode = typia.protobuf.createEncode<MyObj>();
+console.log(
+  encode({
+    private: true,
+  }),
+);
diff --git a/errors/package.json b/errors/package.json
index 988d0631b2..212373f969 100644
--- a/errors/package.json
+++ b/errors/package.json
@@ -32,6 +32,6 @@
     "typescript": "^5.3.2"
   },
   "dependencies": {
-    "typia": "../typia-6.10.4-dev.20240925.tgz"
+    "typia": "../typia-6.11.1.tgz"
   }
 }
\ No newline at end of file
diff --git a/src/factories/ProtobufFactory.ts b/src/factories/ProtobufFactory.ts
index 8eb4fc58db..f97731e0aa 100644
--- a/src/factories/ProtobufFactory.ts
+++ b/src/factories/ProtobufFactory.ts
@@ -9,8 +9,6 @@ import { TransformerError } from "../transformers/TransformerError";
 
 import { ValidationPipe } from "../typings/ValidationPipe";
 
-import { Escaper } from "../utils/Escaper";
-
 import { MetadataCollection } from "./MetadataCollection";
 import { MetadataFactory } from "./MetadataFactory";
 
@@ -167,18 +165,6 @@ export namespace ProtobufFactory {
       noSupport(
         "object type with mixed static and dynamic key typed properties. Keep statics or dynamic only.",
       );
-    // STATIC PROPERTY, BUT INVALID KEY NAME
-    if (
-      meta.objects.length &&
-      meta.objects.some((obj) =>
-        obj.properties.some(
-          (p) =>
-            p.key.isSoleLiteral() === true &&
-            Escaper.variable(p.key.getSoleLiteral()!) === false,
-        ),
-      )
-    )
-      noSupport(`object type with invalid static key name.`);
     // DYNAMIC OBJECT, BUT PROPERTY VALUE TYPE IS ARRAY
     if (
       meta.objects.length &&
diff --git a/test-esm/package.json b/test-esm/package.json
index aed685e238..5855452a43 100644
--- a/test-esm/package.json
+++ b/test-esm/package.json
@@ -36,6 +36,6 @@
     "typescript": "^5.4.5"
   },
   "dependencies": {
-    "typia": "../typia-6.10.4-dev.20240925.tgz"
+    "typia": "../typia-6.11.1.tgz"
   }
 }
\ No newline at end of file
diff --git a/test/package.json b/test/package.json
index 554ba147dc..c5e6816f4e 100644
--- a/test/package.json
+++ b/test/package.json
@@ -52,6 +52,6 @@
     "suppress-warnings": "^1.0.2",
     "tstl": "^3.0.0",
     "uuid": "^9.0.1",
-    "typia": "../typia-6.10.4-dev.20240925.tgz"
+    "typia": "../typia-6.11.1.tgz"
   }
 }
\ No newline at end of file
diff --git a/test/src/features/issues/test_issue_1321_private_key_in_protobuf.ts b/test/src/features/issues/test_issue_1321_private_key_in_protobuf.ts
new file mode 100644
index 0000000000..d7064d1457
--- /dev/null
+++ b/test/src/features/issues/test_issue_1321_private_key_in_protobuf.ts
@@ -0,0 +1,16 @@
+import typia from "typia";
+
+import { TestValidator } from "../../helpers/TestValidator";
+
+type MyObj = {
+  private: boolean | null;
+};
+
+export const test_issue_1321_private_key_in_protobuf = (): void => {
+  const input: MyObj = {
+    private: true,
+  };
+  const encoded: Uint8Array = typia.protobuf.encode<MyObj>(input);
+  const decoded: MyObj = typia.protobuf.decode<MyObj>(encoded);
+  TestValidator.equals("decoded")(decoded)(input);
+};