diff --git a/Dockerfile b/Dockerfile
index 9cac362..b3fc1bd 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -57,10 +57,14 @@ COPY docs/ ./docs/
 COPY pyproject.toml .
 COPY README.md .
 
-# Create non-root user matching the host uid/gid (passed via build args)
+# Create non-root user matching the host uid/gid (passed via build args).
+# ubuntu:24.04 ships a default 'ubuntu' user/group at uid/gid 1000, so remove
+# it first to free those ids before creating astrai.
 ARG USER_UID=1000
 ARG USER_GID=1000
-RUN groupadd -g "${USER_GID}" astrai \
+RUN userdel -r ubuntu 2>/dev/null || true \
+    && groupdel ubuntu 2>/dev/null || true \
+    && groupadd -g "${USER_GID}" astrai \
     && useradd -m -u "${USER_UID}" -g astrai astrai \
     && chown -R astrai:astrai /app
 ENV HOME=/home/astrai