diff --git a/Dockerfile b/Dockerfile
index 10dab0e..eb7f98e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -11,6 +11,7 @@ RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
 # Install dependencies
 RUN echo "deb [ allow-insecure=yes ] http://apt.postgresql.org/pub/repos/apt/ bionic-pgdg main" >> /etc/apt/sources.list.d/pgdg.list \
   && apt-get update \
+  && apt-get install -y apt-transport-https ca-certificates \
   && apt-get install -y --no-install-recommends --allow-unauthenticated \
   apache2 \
   apache2-dev \
@@ -70,8 +71,6 @@ RUN echo "deb [ allow-insecure=yes ] http://apt.postgresql.org/pub/repos/apt/ bi
 RUN adduser --disabled-password --gecos "" renderer
 USER renderer
 
-ENV GIT_SSL_NO_VERIFY=true
-
 # Install latest osm2pgsql
 RUN mkdir /home/renderer/src
 WORKDIR /home/renderer/src
@@ -106,14 +105,12 @@ WORKDIR /home/renderer/src
 RUN git clone https://github.com/gravitystorm/openstreetmap-carto.git
 WORKDIR /home/renderer/src/openstreetmap-carto
 USER root
-RUN npm config set strict-ssl=false \
-  && npm install -g carto
+RUN npm install -g carto
 USER renderer
 RUN carto project.mml > mapnik.xml
 
 # Load shapefiles
 WORKDIR /home/renderer/src/openstreetmap-carto
-ENV PYTHONHTTPSVERIFY=0
 RUN scripts/get-shapefiles.py
 
 # Configure renderd
diff --git a/README.md b/README.md
index 3ead79a..1ac61e1 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,21 @@ The database use the autovacuum feature by default. This behavior can be changed
 
     docker run -p 80:80 -e AUTOVACUUM=off -v openstreetmap-data:/var/lib/postgresql/10/main -d overv/openstreetmap-tile-server
 
+## Troubleshooting
+
+### ERROR: could not resize shared memory segment
+
+If you encounter such entries in the log, it will mean that the default shared memory limit (64 MB) is too low for the container and it should be raised:
+
+    renderd[126]: ERROR: failed to render TILE ajt 6 32-39 16-23,
+    renderd[126]: reason: Postgis Plugin: ERROR: could not resize shared memory segment
+
+To raise it use `--shm-size` parameter. For example:
+
+    docker run -p 80:80 -v openstreetmap-data:/var/lib/postgresql/10/main --shm-size="192m" -d overv/openstreetmap-tile-server run
+
+For too high values you may notice excessive CPU load and memory usage. It might be that you will have to experimentally find the best values for yourself.
+
 ## License
 
 ```