diff --git a/libs/langchain-google-common/src/chat_models.ts b/libs/langchain-google-common/src/chat_models.ts
index 382991a41362..a345497c0d8f 100644
--- a/libs/langchain-google-common/src/chat_models.ts
+++ b/libs/langchain-google-common/src/chat_models.ts
@@ -189,15 +189,15 @@ export abstract class ChatGoogleBase<AuthOptions>
 
   topK = 40;
 
-  presencePenalty = undefined;
+  presencePenalty: number;
 
-  frequencyPenalty = undefined;
+  frequencyPenalty: number;
 
   stopSequences: string[] = [];
 
-  logprobs: false;
+  logprobs: boolean = false;
 
-  topLogprobs: 0;
+  topLogprobs: number = 0;
 
   safetySettings: GoogleAISafetySetting[] = [];