diff --git a/Dockerfile b/Dockerfile
index 8e8716fa7c75c4ca59aa75637174b5a9828f5254..b0c8c55b56214f2f94917ee525a693b7f7e6bc89 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -89,7 +89,7 @@ RUN mkdir -p build_coin && \
     cmake -DCMAKE_BUILD_TYPE=Debug \
           -DCOIN_BUILD_TESTS=0 \
           -DCMAKE_CXX_STANDARD=17 \
-          -DCMAKE_INSTALL_PREFIX=$INSTALL_DIR \
+          -DCMAKE_INSTALL_PREFIX=${INSTALL_DIR} \
           ../coin && \
     make -j4 && \
     make install && \
@@ -106,7 +106,8 @@ RUN pwd; ls && \
      cd build && \
      cmake -DCMAKE_BUILD_TYPE=Debug \
            -DSOQT_BUILD_TESTS=0 \
-           -DCMAKE_INSTALL_PREFIX=$INSTALL_DIR ../soqt && \
+           -DCMAKE_INSTALL_PREFIX=${INSTALL_DIR} \
+           ../soqt && \
      make -j8 && \
      make install && \
      cd ../../ && \