diff --git a/app/api/voice/chat/route.ts b/app/api/voice/chat/route.ts
index 0c36aae..35942d1 100644
--- a/app/api/voice/chat/route.ts
+++ b/app/api/voice/chat/route.ts
@@ -55,7 +55,7 @@ function toAnthropicTools(tools: any[]): any[] {
 function historyToAnthropicMessages(history: HistoryMessage[]): any[] {
   const result: any[] = []
   for (const msg of history) {
-    if (msg.role === 'system') continue // skip, goes in system field
+    if ((msg.role as string) === 'system') continue // skip, goes in system field
     if (msg.role === 'user') {
       result.push({ role: 'user', content: msg.content || '' })
     } else if (msg.role === 'assistant') {