diff --git a/pinentry-wrapper b/pinentry-wrapper
index 6dd72c5..b017edb 100755
--- a/pinentry-wrapper
+++ b/pinentry-wrapper
@@ -32,7 +32,7 @@ done
 
 # export DISPLAY if pinentry is meant to be run on a different display
 # check the KDE_FULL_SESSION variable otherwise
-if [ -n "$display" -a "$DISPLAY" != "$display" ]; then
+if [ -n "$display" ] && [ "$DISPLAY" != "$display" ]; then
     export DISPLAY="$display"
 elif [ -n "$KDE_FULL_SESSION" ]; then
     kde_running=1
@@ -43,7 +43,7 @@ fi
 type xprop >/dev/null 2>/dev/null
 XPROP=$?
 
-if [ -n "$DISPLAY" -a $XPROP -eq 0 ]; then
+if [ -n "$DISPLAY" ] && [ $XPROP -eq 0 ]; then
     xprop -root | grep "^KDE_FULL_SESSION" >/dev/null 2>/dev/null
     if test $? -eq 0; then
         kde_running=1
@@ -56,19 +56,19 @@ if [ -n "$PINENTRY_BINARY" ];
 then
 	export PINENTRY_BINARY="$PINENTRY_BINARY"
 # if KDE is detected and pinentry-qt exists, use pinentry-qt
-elif [ -n "$kde_running" -a -x /usr/bin/pinentry-qt ]
+elif [ -n "$kde_running" ] && [ -x /usr/bin/pinentry-qt ]
 then
 	export PINENTRY_BINARY="/usr/bin/pinentry-qt"
 # otherwise test if pinentry-gnome3 is installed
-elif [ -n "$DISPLAY" -a -x /usr/bin/pinentry-gnome3 ]
+elif [ -n "$DISPLAY" ] && [ -x /usr/bin/pinentry-gnome3 ]
 then
 	export PINENTRY_BINARY="/usr/bin/pinentry-gnome3"
 # otherwise test if pinentry-gtk-2 is installed
-elif [ -n "$DISPLAY" -a -x /usr/bin/pinentry-gtk-2 ]
+elif [ -n "$DISPLAY" ] && [ -x /usr/bin/pinentry-gtk-2 ]
 then
 	export PINENTRY_BINARY="/usr/bin/pinentry-gtk-2"
 # otherwise test if pinentry-qt exists although KDE is not detected
-elif [ -n "$DISPLAY" -a -x /usr/bin/pinentry-qt ]
+elif [ -n "$DISPLAY" ] && [ -x /usr/bin/pinentry-qt ]
 then
 	export PINENTRY_BINARY="/usr/bin/pinentry-qt"
 # use pinentry-tty if installed