diff --git a/misc/userscripts/qutedmenu b/misc/userscripts/qutedmenu
index de1b8d641..cc5a44413 100755
--- a/misc/userscripts/qutedmenu
+++ b/misc/userscripts/qutedmenu
@@ -37,7 +37,7 @@ get_selection() {
 # https://github.com/halfwit/dotfiles/blob/master/.config/dmenu/font
 [[ -s $confdir/dmenu/font ]] && read -r font < "$confdir"/dmenu/font
 
-[[ $font ]] && opts+=(-fn "$font")
+[[ -n $font ]] && opts+=(-fn "$font")
 
 # shellcheck source=/dev/null
 [[ -s $optsfile ]] && source "$optsfile"
@@ -46,7 +46,7 @@ url=$(get_selection)
 url=${url/*http/http}
 
 # If no selection is made, exit (escape pressed, e.g.)
-[[ ! $url ]] && exit 0
+[[ -z $url ]] && exit 0
 
 case $1 in
     open) printf '%s' "open $url" >> "$QUTE_FIFO" || qutebrowser "$url" ;;
diff --git a/scripts/dev/ci/travis_install.sh b/scripts/dev/ci/travis_install.sh
index 18f5aa9ec..c736a01d3 100644
--- a/scripts/dev/ci/travis_install.sh
+++ b/scripts/dev/ci/travis_install.sh
@@ -71,7 +71,7 @@ EOF
 
 set -e
 
-if [[ $DOCKER ]]; then
+if [[ -n $DOCKER ]]; then
     exit 0
 elif [[ $TRAVIS_OS_NAME == osx ]]; then
     # Disable App Nap
diff --git a/scripts/dev/ci/travis_run.sh b/scripts/dev/ci/travis_run.sh
index a287e844e..4e338221f 100644
--- a/scripts/dev/ci/travis_run.sh
+++ b/scripts/dev/ci/travis_run.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
 
-if [[ $DOCKER ]]; then
+if [[ -n $DOCKER ]]; then
     docker run \
            --privileged \
            -v "$PWD:/outside" \