diff --git a/Dockerfile b/Dockerfile
index fa11dd55..4418b380 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -56,9 +56,11 @@ RUN chown -R 999:999 /srv/ && chown -R 999:999 /etc/apache2/
 # maps
 COPY  --chown=999:999 . /srv/mapserver/
 RUN for i in /srv/mapserver/*.map; do echo $i; done
+
 RUN : "${MAP_URL:?MAP_URL not set}" \
  && : "${LEGEND_URL:?LEGEND_URL not set}" \
- && for i in /srv/mapserver/*.map; do sed -i 's#MAP_URL_REPLACE#'"$MAP_URL"'#g' $i ;  sed -i 's#LEGEND_URL_REPLACE#'"$LEGEND_URL"'#g' $i; done
+ && find /srv/mapserver /srv/mapserver/referentiekaarten -maxdepth 1 -type f -name "*.map" -exec sed -i -e "s#MAP_URL_REPLACE#${MAP_URL}#g" -e "s#LEGEND_URL_REPLACE#${LEGEND_URL}#g" {} +
+
 RUN rm -rf /srv/mapserver/private
 RUN python3 /srv/mapserver/tools/make_indexjson.py /srv/mapserver/*.map > /srv/mapserver/index.json
 
diff --git a/Dockerfile.private b/Dockerfile.private
index 74f0f787..4b98a120 100644
--- a/Dockerfile.private
+++ b/Dockerfile.private
@@ -2,6 +2,13 @@ ARG BASE_IMAGE
 
 FROM ${BASE_IMAGE}
 
+# build-time inputs
+ARG EXTRA_ARG1
+ARG EXTRA_ARG2
+
+ENV MAP_URL="${EXTRA_ARG1:-http://localhost:8383}" \
+    LEGEND_URL="${EXTRA_ARG2:-http://localhost:8383}"
+
 # used by make_mapfile_config.py to include private mapfiles in sld config
 ENV ACCESS_SCOPE private
 USER root
@@ -10,4 +17,8 @@ USER root
 # private variety.
 RUN rm -rf /srv/mapserver/private
 COPY --chown=999:999 /private/ /srv/mapserver/
+RUN : "${MAP_URL:?MAP_URL not set}" \
+ && : "${LEGEND_URL:?LEGEND_URL not set}" \
+ && find /srv/mapserver -maxdepth 1 -type f -name "*.map" -exec sed -i -e "s#MAP_URL_REPLACE#${MAP_URL}#g" -e "s#LEGEND_URL_REPLACE#${LEGEND_URL}#g" {} +
+
 USER www-data
diff --git a/Dockerfile.topografie b/Dockerfile.topografie
index bbf220ee..9fea3017 100644
--- a/Dockerfile.topografie
+++ b/Dockerfile.topografie
@@ -2,9 +2,20 @@ ARG BASE_IMAGE
 
 FROM ${BASE_IMAGE}
 
+# build-time inputs
+ARG EXTRA_ARG1
+ARG EXTRA_ARG2
+
+ENV MAP_URL="${EXTRA_ARG1:-http://localhost:8383}" \
+    LEGEND_URL="${EXTRA_ARG2:-http://localhost:8383}"
+
 USER root
 # Copy referentiekaarten mapfiles into the root dir so they will be served
 
 RUN rm -rf /srv/mapserver/private
 COPY --chown=999:999 /referentiekaarten/ /srv/mapserver/
+RUN : "${MAP_URL:?MAP_URL not set}" \
+ && : "${LEGEND_URL:?LEGEND_URL not set}" \
+ && find /srv/mapserver -maxdepth 1 -type f -name "*.map" -exec sed -i -e "s#MAP_URL_REPLACE#${MAP_URL}#g" -e "s#LEGEND_URL_REPLACE#${LEGEND_URL}#g" {} +
+
 USER www-data