diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 2e86cf5..e5f9c56 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -178,9 +178,8 @@
 RUN tar -xzf v1.2.2.tar.gz
 RUN cp -a cereal-1.2.2/include/cereal/ /usr/local/include/
 
-RUN curl -L -O https://github.com/nlohmann/json/releases/download/v3.0.1/json.hpp
-RUN mkdir /usr/local/include/nlohmann/
-RUN cp -a json.hpp /usr/local/include/nlohmann/
+RUN mkdir /usr/local/include/nlohmann/ && \
+curl -L -o /usr/local/include/nlohmann/json.hpp https://github.com/nlohmann/json/releases/download/v3.0.1/json.hpp
 
 RUN curl -L -O https://dl.bintray.com/boostorg/release/1.66.0/source/boost_1_66_0.tar.bz2
 RUN tar --bzip2 -xf boost_1_66_0.tar.bz2