diff --git a/src/proxy/middleware/request/preprocessors/transform-outbound-payload.ts b/src/proxy/middleware/request/preprocessors/transform-outbound-payload.ts
index 42da63e..9cb18df 100644
--- a/src/proxy/middleware/request/preprocessors/transform-outbound-payload.ts
+++ b/src/proxy/middleware/request/preprocessors/transform-outbound-payload.ts
@@ -59,15 +59,12 @@ function applyMistralPromptFixes(req: Request): void {
     // don't properly handle the differences. We will try to validate the
     // mistral prompt and try to fix it if it fails. It will be re-validated
     // after this function returns.
-    const result = API_REQUEST_VALIDATORS["mistral-ai"].safeParse(req.body);
-    if (!result.success) {
-      const messages = req.body.messages;
-      req.body.messages = fixMistralPrompt(messages);
-      req.log.info(
-        { old: messages.length, new: req.body.messages.length },
-        "Applied Mistral chat prompt fixes."
-      );
-    }
+    const result = API_REQUEST_VALIDATORS["mistral-ai"].parse(req.body);
+    req.body.messages = fixMistralPrompt(result.messages);
+    req.log.info(
+      { n: req.body.messages.length, prev: result.messages.length },
+      "Applied Mistral chat prompt fixes."
+    );
 
     // If the prompt relies on `prefix: true` for the last message, we need to
     // convert it to a text completions request because Mistral support for
diff --git a/src/proxy/middleware/response/streaming/aggregators/mistral-chat.ts b/src/proxy/middleware/response/streaming/aggregators/mistral-chat.ts
index 9ca6f32..5c5099c 100644
--- a/src/proxy/middleware/response/streaming/aggregators/mistral-chat.ts
+++ b/src/proxy/middleware/response/streaming/aggregators/mistral-chat.ts
@@ -1,17 +1,5 @@
 import { OpenAIChatCompletionStreamEvent } from "../index";
 
-/*
-    "choices": [
-        {
-            "index": 0,
-            "message": {
-                "role": "assistant",
-                "content": "Genshin Impact is an action role-play"
-            },
-            "stop_reason": "length"
-        }
-    ],
- */
 export type MistralChatCompletionResponse = {
   choices: {
     index: number;
diff --git a/src/proxy/middleware/response/streaming/event-aggregator.ts b/src/proxy/middleware/response/streaming/event-aggregator.ts
index dd856f0..1311fd1 100644
--- a/src/proxy/middleware/response/streaming/event-aggregator.ts
+++ b/src/proxy/middleware/response/streaming/event-aggregator.ts
@@ -55,9 +55,7 @@ export class EventAggregator {
       let openAIEvent: OpenAIChatCompletionStreamEvent | undefined;
       switch (this.requestFormat) {
         case "anthropic-text":
-          if (!eventIsAnthropicV2Event(event)) {
-            throw new Error(`Bad event for Anthropic V2 SSE aggregation`);
-          }
+          assertIsAnthropicV2Event(event);
           openAIEvent = anthropicV2ToOpenAI({
             data: `event: completion\ndata: ${JSON.stringify(event)}\n\n`,
             lastPosition: -1,
@@ -67,9 +65,7 @@ export class EventAggregator {
           })?.event;
           break;
         case "mistral-ai":
-          if (!eventIsMistralChatEvent(event)) {
-            throw new Error(`Bad event for Mistral SSE aggregation`);
-          }
+          assertIsMistralChatEvent(event);
           openAIEvent = mistralAIToOpenAI({
             data: `data: ${JSON.stringify(event)}\n\n`,
             lastPosition: -1,
@@ -120,12 +116,16 @@ function eventIsOpenAIEvent(
   return event?.object === "chat.completion.chunk";
 }
 
-function eventIsAnthropicV2Event(event: any): event is AnthropicV2StreamEvent {
-  return event?.completion;
+function assertIsAnthropicV2Event(event: any): asserts event is AnthropicV2StreamEvent {
+  if (!event?.completion) {
+    throw new Error(`Bad event for Anthropic V2 SSE aggregation`);
+  }
 }
 
-function eventIsMistralChatEvent(
+function assertIsMistralChatEvent(
   event: any
-): event is MistralChatCompletionEvent {
-  return event?.choices;
+): asserts event is MistralChatCompletionEvent {
+  if (!event?.choices) {
+    throw new Error(`Bad event for Mistral SSE aggregation`);
+  }
 }
diff --git a/src/shared/api-schemas/mistral-ai.ts b/src/shared/api-schemas/mistral-ai.ts
index a1e4956..2fa7131 100644
--- a/src/shared/api-schemas/mistral-ai.ts
+++ b/src/shared/api-schemas/mistral-ai.ts
@@ -27,7 +27,6 @@ const MistralMessagesSchema = z.array(MistralChatMessageSchema).refine(
 // https://docs.mistral.ai/api#operation/createChatCompletion
 const BaseMistralAIV1CompletionsSchema = z.object({
   model: z.string(),
-  // One must be provided, checked in a refinement
   messages: MistralMessagesSchema.optional(),
   prompt: z.string().optional(),
   temperature: z.number().optional().default(0.7),