diff --git a/src/fallback.ts b/src/fallback.ts
index f52f87bd6..e074fa315 100644
--- a/src/fallback.ts
+++ b/src/fallback.ts
@@ -134,7 +134,7 @@ export class GrpcClient {
   }
 
   loadProtoJSON(json: protobuf.INamespace, ignoreCache = false) {
-    const hash = objectHash(json);
+    const hash = objectHash(json).toString();
     const cached = GrpcClient.protoCache.get(hash);
     if (cached && !ignoreCache) {
       return cached;
diff --git a/src/grpc.ts b/src/grpc.ts
index 4e64f627f..5fde573d2 100644
--- a/src/grpc.ts
+++ b/src/grpc.ts
@@ -292,7 +292,7 @@ export class GrpcClient {
   }
 
   loadProtoJSON(json: protobuf.INamespace, ignoreCache = false) {
-    const hash = objectHash(json);
+    const hash = objectHash(json).toString();
     const cached = GrpcClient.protoCache.get(hash);
     if (cached && !ignoreCache) {
       return cached;