diff --git a/src/chatgpt-api.ts b/src/chatgpt-api.ts
index 696367c8f..b2ce8b267 100644
--- a/src/chatgpt-api.ts
+++ b/src/chatgpt-api.ts
@@ -231,7 +231,6 @@ export class ChatGPTAPI {
                     }
 
                     result.detail = response
-
                     onProgress?.(result)
                   }
                 } catch (err) {
@@ -299,15 +298,21 @@ export class ChatGPTAPI {
       }
     ).then(async (message) => {
       if (message.detail && !message.detail.usage) {
-        const promptTokens = numTokens
-        const completionTokens = await this._getTokenCount(message.text)
-        message.detail.usage = {
-          prompt_tokens: promptTokens,
-          completion_tokens: completionTokens,
-          total_tokens: promptTokens + completionTokens,
-          estimated: true
+        try {
+          const promptTokens = numTokens
+          const completionTokens = await this._getTokenCount(message.text)
+          message.detail.usage = {
+            prompt_tokens: promptTokens,
+            completion_tokens: completionTokens,
+            total_tokens: promptTokens + completionTokens,
+            estimated: true
+          }
+        } catch (err) {
+          // TODO: this should really never happen, but if it does,
+          // we should handle notify the user gracefully
         }
       }
+
       return this._upsertMessage(message).then(() => message)
     })
 
diff --git a/src/types.ts b/src/types.ts
index 95874ade3..2c1ad218d 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -61,16 +61,6 @@ export type SendMessageBrowserOptions = {
   abortSignal?: AbortSignal
 }
 
-interface CreateChatCompletionStreamResponse
-  extends openai.CreateChatCompletionDeltaResponse {
-  usage: CreateCompletionStreamResponseUsage
-}
-
-interface CreateCompletionStreamResponseUsage
-  extends openai.CreateCompletionResponseUsage {
-  estimated: true
-}
-
 export interface ChatMessage {
   id: string
   text: string
@@ -100,6 +90,16 @@ export type GetMessageByIdFunction = (id: string) => Promise<ChatMessage>
 /** Upserts a chat message to a store. */
 export type UpsertMessageFunction = (message: ChatMessage) => Promise<void>
 
+export interface CreateChatCompletionStreamResponse
+  extends openai.CreateChatCompletionDeltaResponse {
+  usage: CreateCompletionStreamResponseUsage
+}
+
+export interface CreateCompletionStreamResponseUsage
+  extends openai.CreateCompletionResponseUsage {
+  estimated: true
+}
+
 /**
  * https://chat.openapi.com/backend-api/conversation
  */