diff --git a/src/api/providers/deepseek.ts b/src/api/providers/deepseek.ts
index 43aefe7117..763e1ae68f 100644
--- a/src/api/providers/deepseek.ts
+++ b/src/api/providers/deepseek.ts
@@ -51,7 +51,7 @@ export class DeepSeekHandler implements ApiHandler {
 				}
 			}
 
-			if ("reasoning_content" in delta && delta.reasoning_content) {
+			if (delta && "reasoning_content" in delta && delta.reasoning_content) {
 				yield {
 					type: "reasoning",
 					reasoning: (delta.reasoning_content as string | undefined) || "",
diff --git a/src/api/providers/openai.ts b/src/api/providers/openai.ts
index e70273041f..fd73abb567 100644
--- a/src/api/providers/openai.ts
+++ b/src/api/providers/openai.ts
@@ -56,7 +56,7 @@ export class OpenAiHandler implements ApiHandler {
 				}
 			}
 
-			if ("reasoning_content" in delta && delta.reasoning_content) {
+			if (delta && "reasoning_content" in delta && delta.reasoning_content) {
 				yield {
 					type: "reasoning",
 					reasoning: (delta.reasoning_content as string | undefined) || "",