diff --git a/scripts/install_R_source.sh b/scripts/install_R_source.sh
index 9d5159d4..4e5a8281 100755
--- a/scripts/install_R_source.sh
+++ b/scripts/install_R_source.sh
@@ -159,7 +159,7 @@ rm -rf "R.tar.gz"
 cp /usr/bin/checkbashisms /usr/local/bin/checkbashisms
 
 # shellcheck disable=SC2086
-if [ "${PURGE_BUILDDEPS}" == "true" ]; then
+if [ "${PURGE_BUILDDEPS}" != "false" ]; then
     apt-get remove --purge -y ${BUILDDEPS}
 fi
 apt-get autoremove -y
diff --git a/scripts/setup_R.sh b/scripts/setup_R.sh
index 9c68cc7c..c2e8202a 100755
--- a/scripts/setup_R.sh
+++ b/scripts/setup_R.sh
@@ -10,7 +10,7 @@
 set -e
 
 CRAN=${1:-${CRAN:-"https://cran.r-project.org"}}
-PURGE_BUILDDEPS=${PURGE_BUILDDEPS=-"true"}
+PURGE_BUILDDEPS=${PURGE_BUILDDEPS:-"true"}
 
 ARCH=$(uname -m)
 
@@ -69,7 +69,7 @@ if [ ! -x "$(command -v r)" ]; then
 
     # Clean up
     # shellcheck disable=SC2086
-    if [ "${PURGE_BUILDDEPS}" == "true" ]; then
+    if [ "${PURGE_BUILDDEPS}" != "false" ]; then
         apt-get remove --purge -y ${BUILDDEPS}
     fi
     apt-get autoremove -y