diff --git a/resources/apply_format.sh b/resources/apply_format.sh
index 4191d10..2e12837 100755
--- a/resources/apply_format.sh
+++ b/resources/apply_format.sh
@@ -26,7 +26,7 @@
 #
 set -e
 
-if [ -z "$SELFDIR" ];
+if [[ -z "$SELFDIR" ]];
 then
     echo "SELFDIR not defined"
     exit 1
diff --git a/resources/apply_license.sh b/resources/apply_license.sh
index d4fd8fa..8fd6371 100755
--- a/resources/apply_license.sh
+++ b/resources/apply_license.sh
@@ -30,7 +30,7 @@
 #
 set -e
 
-if [ -z "$SELFDIR" ];
+if [[ -z "$SELFDIR" ]];
 then
   echo "SELFDIR not defined"
   exit 1
diff --git a/resources/check_format.sh b/resources/check_format.sh
index 231e353..78f3c2a 100755
--- a/resources/check_format.sh
+++ b/resources/check_format.sh
@@ -22,7 +22,7 @@
 ##
 set -e
 
-if [ -z "$SELFDIR" ];
+if [[ -z "$SELFDIR" ]];
 then
     echo "$SELFDIR not defined"
     exit 1
@@ -36,7 +36,7 @@ echo "Check format from root: $SELFDIR"
 ./resources/apply_license.sh
 
 changed=$(git status --porcelain=1)
-if [ -n "${changed}" ]; then
+if [[ -n "${changed}" ]]; then
   echo "Error: Files changed after formatting:"
   git diff
   exit 1
diff --git a/resources/deps.sh b/resources/deps.sh
index ca99488..11e9a96 100755
--- a/resources/deps.sh
+++ b/resources/deps.sh
@@ -26,7 +26,7 @@
 #
 set -e
 
-if [ -z "$SELFDIR" ]
+if [[ -z "$SELFDIR" ]]
 then
   echo "SELFDIR not defined"
   exit 1
@@ -42,7 +42,7 @@ mkdir -p ${BUILDDIR}
 
 # Note: This checks for existence of qcbor, and if exists
 # then skips rebuilding it.
-if [ ! -e ${DESTDIR}${PREFIX}/include/qcbor ]
+if [[ ! -e ${DESTDIR}${PREFIX}/include/qcbor ]]
 then
   echo "Building QCBOR..."
   pushd ${DEPSDIR}/QCBOR
@@ -59,7 +59,7 @@ fi
 
 # Note: This checks for existence of this path, skips building
 # if already exists.
-if [ ! -e ${DESTDIR}${PREFIX}/include/m-lib ]
+if [[ ! -e ${DESTDIR}${PREFIX}/include/m-lib ]]
 then
   echo "Building MLIB..."
   rsync --recursive ${DEPSDIR}/mlib/ ${BUILDDIR}/mlib/
@@ -73,7 +73,7 @@ fi
 
 
 # Note: Skips building unity if this path already exists.
-if [ ! -e ${DESTDIR}${PREFIX}/include/unity ]
+if [[ ! -e ${DESTDIR}${PREFIX}/include/unity ]]
 then
   echo "Building Unity..."
   pushd ${DEPSDIR}/unity
diff --git a/resources/prep.sh b/resources/prep.sh
index f4d6d9d..70a1655 100755
--- a/resources/prep.sh
+++ b/resources/prep.sh
@@ -26,7 +26,7 @@
 #
 set -e
 
-if [ -z "$SELFDIR" ]
+if [[ -z "$SELFDIR" ]]
 then
   echo "SELFDIR not defined"
   exit 1