diff --git a/common/src/main/kotlin/com/google/ai/client/generativeai/common/server/Types.kt b/common/src/main/kotlin/com/google/ai/client/generativeai/common/server/Types.kt
index 16b25a78..0fa28ff4 100644
--- a/common/src/main/kotlin/com/google/ai/client/generativeai/common/server/Types.kt
+++ b/common/src/main/kotlin/com/google/ai/client/generativeai/common/server/Types.kt
@@ -66,7 +66,7 @@ constructor(@JsonNames("citations") val citationSources: List<CitationSources>)
 data class CitationSources(
   val startIndex: Int = 0,
   val endIndex: Int,
-  val uri: String,
+  val uri: String? = null,
   val license: String? = null,
 )