diff --git a/packages/protobuf-bench/README.md b/packages/protobuf-bench/README.md
index fe1e3f448..737f0a16e 100644
--- a/packages/protobuf-bench/README.md
+++ b/packages/protobuf-bench/README.md
@@ -10,5 +10,5 @@ server would usually do.
 
 | code generator      | bundle size             | minified               | compressed         |
 |---------------------|------------------------:|-----------------------:|-------------------:|
-| protobuf-es         | 88,672 b      | 37,773 b | 9,865 b |
+| protobuf-es         | 88,669 b      | 37,770 b | 9,843 b |
 | protobuf-javascript | 394,384 b  | 288,761 b | 45,123 b |
diff --git a/packages/protobuf/src/private/json-format-common.ts b/packages/protobuf/src/private/json-format-common.ts
index e13b4e439..a1f0d5b0d 100644
--- a/packages/protobuf/src/private/json-format-common.ts
+++ b/packages/protobuf/src/private/json-format-common.ts
@@ -328,7 +328,7 @@ export function makeJsonFormatCommon(
   };
 }
 
-function debugJsonValue(json: JsonValue): string {
+function debugJsonValue(json: unknown): string {
   if (json === null) {
     return "null";
   }
@@ -338,7 +338,7 @@ function debugJsonValue(json: JsonValue): string {
     case "string":
       return json.length > 100 ? "string" : `"${json.split('"').join('\\"')}"`;
     default:
-      return json.toString();
+      return String(json);
   }
 }