diff --git a/generativeai/src/main/java/com/google/ai/client/generativeai/type/CountTokensResponse.kt b/generativeai/src/main/java/com/google/ai/client/generativeai/type/CountTokensResponse.kt
index a2d9255e..59a94c24 100644
--- a/generativeai/src/main/java/com/google/ai/client/generativeai/type/CountTokensResponse.kt
+++ b/generativeai/src/main/java/com/google/ai/client/generativeai/type/CountTokensResponse.kt
@@ -21,6 +21,6 @@ package com.google.ai.client.generativeai.type
  *
  * @property totalTokens A count of the number of tokens in the input
  */
-class CountTokensResponse(val totalTokens: Int) {
+class CountTokensResponse(val totalTokens: Int?) {
   operator fun component1() = totalTokens
 }