diff --git a/llmage/llmclient.py b/llmage/llmclient.py
index 824e0f0..01dac20 100644
--- a/llmage/llmclient.py
+++ b/llmage/llmclient.py
@@ -109,7 +109,7 @@ async def write_llmusage(id, llm, userid, usage, params_kw, outdata, sor):
 		"userid": userid,
 		"transno": params_kw.transno,
 		"evalvalue": 0,
-		"usages": usage,
+		"usages": json.dumps(usage),
 		"ioinfo": json.dumps({
 			"input": params_kw,
 			"output": outdata