diff --git a/Dockerfile b/Dockerfile
index 80f74f75..54345758 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,25 +3,35 @@ FROM continuumio/miniconda3:4.9.2
 ARG DEBIAN_FRONTEND=noninteractive
 ARG USER=user
 ARG GROUP=user
-ARG UID=1000
-ARG GID=1000
+ARG UID
+ARG GID
 
 ENV TERM="xterm-256color"
 ENV HOME="/home/user"
 
 RUN set -x \
-  && mkdir -p ${HOME}/data \
-  && addgroup --system --gid ${GID} ${GROUP} \
-  && useradd --system --create-home --home-dir ${HOME} \
-  --shell /bin/bash \
-  --gid ${GROUP} \
-  --groups sudo \
-  --uid ${UID} \
-  ${USER} \
-  && touch ${HOME}.hushlogin
+  && mkdir -p ${HOME}/src \
+  && \
+    if [ -z "$(getent group ${GID})" ]; then \
+      addgroup --system --gid ${GID} ${GROUP}; \
+    else \
+      groupmod -n ${GROUP} $(getent group ${GID} | cut -d: -f1); \
+    fi \
+  && \
+    if [ -z "$(getent passwd ${UID})" ]; then \
+      useradd \
+        --system \
+        --create-home --home-dir ${HOME} \
+        --shell /bin/bash \
+        --gid ${GROUP} \
+        --groups sudo \
+        --uid ${UID} \
+        ${USER}; \
+    fi \
+  && touch ${HOME}/.hushlogin
 
 RUN set -x \
-  && chown -R ${USER}:${GROUP} ${HOME}
+  && chown -R ${UID}:${GID} ${HOME}
 
 COPY environment.yml ${HOME}/src/
 
@@ -30,7 +40,7 @@ WORKDIR ${HOME}/src
 RUN set -x \
   && conda env create docs.nextstrain.org
 
-USER ${USER}
+USER ${UID}
 
 RUN set -x \
   && conda init bash \
diff --git a/Makefile b/Makefile
index ff75d6ab..cb5f9ef3 100644
--- a/Makefile
+++ b/Makefile
@@ -22,7 +22,11 @@ help:
 .ONESHELL:
 docker-html:
 	set -euox
-	docker build -t nextstrain-docs-builder --network=host .
+	docker build -t nextstrain-docs-builder \
+	--network=host \
+	--build-arg UID=$(shell id -u) \
+	--build-arg GID=$(shell id -g) \
+	.
 	docker run -it --rm \
 	--name=nextstrain-docs-builder-$(shell date +%s) \
 	--init \