diff --git a/commonsh/10_pager b/commonsh/10_pager
index 6e3a508..c33adfb 100755
--- a/commonsh/10_pager
+++ b/commonsh/10_pager
@@ -7,7 +7,7 @@ export PAGER
 if [ $PAGER = less ] ; then
 	for lesspipe in lesspipe lesspipe.sh ; do
 		lesspipe_test=`command -v ${lesspipe} 2>/dev/null`
-		if [ -n $lesspipe_test ] ; then
+		if [ -n "${lesspipe_test}" ] ; then
 			LESSOPEN="| ${lesspipe_test} %s" && break
 			export LESSOPEN
 		fi
diff --git a/ksh/prompt b/ksh/prompt
index 5479b99..f97779b 100755
--- a/ksh/prompt
+++ b/ksh/prompt
@@ -1,4 +1,4 @@
-if [ ! $USER ] ; then
+if [ -z "${USER}" ] ; then
 	USER=$LOGNAME
 fi
 
diff --git a/zsh/prompt b/zsh/prompt
index de19ff7..5a1ab0b 100755
--- a/zsh/prompt
+++ b/zsh/prompt
@@ -1,5 +1,5 @@
 # prompt
-if [ -z ${SSH_TTY} ] ; then
+if [ -z "${SSH_TTY}" ] ; then
 	PROMPT=$'%{\e[01;32m%}%n@%m %{\e[01;34m%}%~ %(?..%{\e[01;31m%})%(!.#.$) %{\e[00;00m%}'
 	RPROMPT=$'%1(j.%{\e[00;36m%}[%j].)%{\e[01;33m%}[%t]%{\e[00;00m%}'
 else