diff --git a/scripts/est_examples.sh b/scripts/est_examples.sh
index 5e6f38c..b931fda 100755
--- a/scripts/est_examples.sh
+++ b/scripts/est_examples.sh
@@ -64,7 +64,7 @@ EOF
 prepend() {
 	var="$1"
 	extra="$2"
-	eval "val=\$$var"
+	eval "val=\${$var:-}"
 	
 	if [ -n "$val" ]
 		then
diff --git a/scripts/shared_script b/scripts/shared_script
index b159134..2732699 100644
--- a/scripts/shared_script
+++ b/scripts/shared_script
@@ -5,7 +5,7 @@
 extend() {
 	var="$1"
 	extra="$2"
-	eval "val=\$$var"
+	eval "val=\${$var:-}"
 	
 	if [ -n "$val" ]
 		then
diff --git a/scripts/shared_setup_sh b/scripts/shared_setup_sh
index 64f0ba9..e0488f4 100644
--- a/scripts/shared_setup_sh
+++ b/scripts/shared_setup_sh
@@ -4,7 +4,7 @@
 extend() {
 	var="$1"
 	extra="$2"
-	eval "val=\$$var"
+	eval "val=\${$var:-}"
 	
 	if [ -n "$val" ]
 		then