diff --git a/Dockerfile b/Dockerfile
index d8b09a3..4aee932 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -6,6 +6,7 @@ WORKDIR /code
 
 ENV BOLOS_ENV /opt/bolos-env
 ENV BOLOS_SDK /opt/bolos-sdk
+ENV BOLOS_VERSION tags/nanos-1552
 
 RUN apt-get update
 
@@ -29,7 +30,7 @@ RUN echo "Install custom clang" && \
 
 RUN echo "Install Ledger Nano S SDK" && \
   git clone https://github.com/LedgerHQ/nanos-secure-sdk.git ${BOLOS_SDK} && \
-  cd ${BOLOS_SDK} && git checkout tags/nanos-1552
+  cd ${BOLOS_SDK} && git checkout ${BOLOS_VERSION}
 
 COPY ./bin/init /usr/local/bin/init
 
diff --git a/README.md b/README.md
index c993c72..108a6b9 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,15 @@ To run an arbitrary command in your project dir:
 docker run -v ${PWD}:/code lukechilds/ledger-sdk 'make clean'
 ```
 
+The following environment variables can be set to customise the build (here
+shown with defaults):
+
+```sh
+docker run \
+	-e "BOLOS_VERSION=tags/nanos-1552" \ # BOLOS SDK git commit/tag/branch to checkout
+	-v ${PWD}:/code lukechilds/ledger-sdk
+```
+
 ## License
 
 MIT © Luke Childs