diff --git a/scripts/install b/scripts/install
index e9d4599..1c7409a 100755
--- a/scripts/install
+++ b/scripts/install
@@ -1,6 +1,5 @@
 #!/bin/bash
-set -e
-# Constants
+set -eu
 
 # Retrieve arguments
 domain=$1
diff --git a/scripts/remove b/scripts/remove
index 3bff0f8..77cab30 100755
--- a/scripts/remove
+++ b/scripts/remove
@@ -1,5 +1,5 @@
 #!/bin/bash
-set -e
+set -u
 
 # supervisord and other Debian dependencies remain installed
 # there is no way to know if they are used by other programs
diff --git a/scripts/upgrade b/scripts/upgrade
index ed9ddba..d51874f 100755
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -1,5 +1,5 @@
 #!/bin/bash
-set -e
+set -eu
 app=$YNH_APP_INSTANCE_NAME