diff --git a/docker/Dockerfile.lambda b/docker/Dockerfile.lambda
index 6c0d677d..404c8529 100644
--- a/docker/Dockerfile.lambda
+++ b/docker/Dockerfile.lambda
@@ -6,7 +6,7 @@ RUN yum update -y && \
 
 ADD requirements.txt .
 RUN pip install -r requirements.txt && rm requirements.txt
-RUN pip install mangum
+RUN pip install mangum==16.0.0
 COPY pr_agent/ ${LAMBDA_TASK_ROOT}/pr_agent/
 
 CMD ["pr_agent.servers.serverless.serverless"]