diff --git a/server/Dockerfile b/server/Dockerfile
index eecf4de..f3fd9fe 100644
--- a/server/Dockerfile
+++ b/server/Dockerfile
@@ -1,4 +1,4 @@
-FROM python:3.14.6-slim
+FROM python:3.15.0b3-slim
 
 ENV DEVPISERVER_SERVERDIR=/devpi/server
 RUN mkdir -p $DEVPISERVER_SERVERDIR && \
diff --git a/server/Dockerfile-alpine b/server/Dockerfile-alpine
index a5328cc..0c6691e 100644
--- a/server/Dockerfile-alpine
+++ b/server/Dockerfile-alpine
@@ -1,4 +1,4 @@
-FROM python:3.14.6-alpine
+FROM python:3.15.0b4-alpine
 
 ENV DEVPISERVER_SERVERDIR=/devpi/server
 RUN mkdir -p $DEVPISERVER_SERVERDIR && \