diff --git a/streamaccumulator.go b/streamaccumulator.go
index 53b7069f..2fcda3c6 100644
--- a/streamaccumulator.go
+++ b/streamaccumulator.go
@@ -163,11 +163,11 @@ func (prev *chatCompletionResponseState) update(chunk ChatCompletionChunk) (just
 	delta := chunk.Choices[0].Delta
 	new := chatCompletionResponseState{}
 	switch {
-	case delta.JSON.Content.Valid():
+	case delta.Content != "":
 		new.state = contentResponseState
-	case delta.JSON.Refusal.Valid():
+	case delta.Refusal != "":
 		new.state = refusalResponseState
-	case delta.JSON.ToolCalls.Valid():
+	case len(delta.ToolCalls) > 0:
 		new.state = toolResponseState
 		new.index = int(delta.ToolCalls[0].Index)
 	default:
diff --git a/streamaccumulator_test.go b/streamaccumulator_test.go
index 6c602842..db871f11 100644
--- a/streamaccumulator_test.go
+++ b/streamaccumulator_test.go
@@ -535,4 +535,4 @@ data: {"id":"chatcmpl-A3Tguz3LSXTHBTY2NAPBCSyfBltxF","object":"chat.completion.c
 
 data: [DONE]
 
-`
+`
\ No newline at end of file