diff --git a/README.md b/README.md
index 1015854..3c583fe 100644
--- a/README.md
+++ b/README.md
@@ -24,14 +24,14 @@ Any feedback appreciated: [contact@artcode.re](mailto:contact@artcode.re)
       * [x] git, failure aware
   * [x] vimrc
 * [x] miaou-bash
-  * [x] error-prone  
+  * [x] friendly error message
   * [x] stacktrace
 * [x] tools
   * [x] semver-git_tag
   * [x] fqdn
 
 ## install
-
+<!-- markdownlint-disable MD013 MD025 -->
 `curl -s https://git.artcode.re/miaou/miaou-bash/raw/branch/main/install.sh | sudo bash && exec bash`
 
 ## upgrade
diff --git a/etc/bash.bashrc b/etc/bash.bashrc
index bddf1b1..517ca4d 100644
--- a/etc/bash.bashrc
+++ b/etc/bash.bashrc
@@ -125,7 +125,7 @@ function __vte_osc7 {
   VTE_INFO="${HOSTNAME:-}"
   if [[ -n ${container_hostname:-} ]]; then
     local host
-    host=$(builtin echo $container_hostname | tr ' ' ':')
+    host=$(builtin echo "$container_hostname" | tr ' ' ':')
     VTE_INFO="$host:$HOSTNAME"
   fi
   printf "\[\033]7;file://%s%s\a\]" "${VTE_INFO}" "$(__vte_urlencode "${PWD}")"
@@ -240,5 +240,11 @@ alias ssu="ss -ntelp | perl -pne 'if(/uid:(\\d+)/){@a=getpwuid(\$1);s/uid:(\\d+)
 alias ssu4="ss -ntel4p | perl -pne 'if(/uid:(\\d+)/){@a=getpwuid(\$1);s/uid:(\\d+)/user:\$a[0]/}' | awk '{ print \$4 \"\\t\\t\" \$7 \"\\t\\t\" \$6 }'"
 
 # Alias definitions.
-[[ -f "/etc/bash.aliases" ]] && source "/etc/bash.aliases" || true
-[[ -f "$HOME/.bash_aliases" ]] && source "$HOME/.bash_aliases" || true
+if [[ -f "/etc/bash.aliases" ]]; then
+  # shellcheck disable=SC1091
+  source "/etc/bash.aliases"
+fi
+if [[ -f "$HOME/.bash_aliases" ]]; then
+  # shellcheck disable=SC1091
+  source "$HOME/.bash_aliases"
+fi
diff --git a/lib/self-upgrade.bash b/lib/self-upgrade.bash
index 6dedc88..5e4c47c 100755
--- a/lib/self-upgrade.bash
+++ b/lib/self-upgrade.bash
@@ -8,7 +8,7 @@
 
 function bootstrap {
   cd "$(mktemp -d)" || exit 3
-  curl -s -O $MAIN_TAR_GZ_URL
+  curl -s -O "$MAIN_TAR_GZ_URL"
   tar -xzf main.tar.gz --directory "$(dirname "$MIAOU_BASH_DIR")"
 
   local source_bin="$MIAOU_BASH_DIR/bin/miaou-bash"
@@ -39,5 +39,5 @@ latest=$("$MIAOU_BASH_DIR/tools/wget_semver" artcode miaou/miaou-bash)
 if [[ "$current" == "$latest" ]]; then
   echo "up-to-date version: $current"
 else
-  self_upgrade 
+  self_upgrade
 fi