diff --git a/src/aioappsrv/app.py b/src/aioappsrv/app.py
index 59f5097..48d1e59 100644
--- a/src/aioappsrv/app.py
+++ b/src/aioappsrv/app.py
@@ -104,8 +104,12 @@ class AppService:
 			json=mx_message(text),
 		) as res:
 			doc = await res.json()
-		self.logger.debug("sent message %s to %s as %s : %s", text, room, mxid, doc)
-		return doc["event_id"]
+		if "event_id" in doc:
+			self.logger.debug("sent message %s to %s as %s : %s", text, room, mxid, doc)
+			return doc["event_id"]
+		else:
+			self.logger.error("failed sending message: %s", doc)
+			raise ValueError(doc)
 
 	async def redact_message(self):
 		raise NotImplementedError