diff --git a/aliases.d/mc b/aliases.d/mc
index bb6d78f..d1393d5 100644
--- a/aliases.d/mc
+++ b/aliases.d/mc
@@ -1,4 +1,4 @@
-if (which mc &> /dev/null); then
+if (command -v mc &> /dev/null); then
   if [ "${TERM}" = "rxvt-unicode" ]; then
     alias mc="TERM=rxvt-unicode-256color mc"
   fi
diff --git a/rc.d/anyenv b/rc.d/anyenv
index f9b25ae..582740f 100644
--- a/rc.d/anyenv
+++ b/rc.d/anyenv
@@ -2,6 +2,6 @@
 
 # git clone https://github.com/riywo/anyenv ${HOME}/.anyenv
 
-if (which anyenv &>/dev/null); then
+if (command -v anyenv &>/dev/null); then
   eval "$(anyenv init -)"
 fi
diff --git a/rc.d/screen b/rc.d/screen
index 45dfd9f..9c025be 100644
--- a/rc.d/screen
+++ b/rc.d/screen
@@ -1,5 +1,5 @@
 # GNU Screen stuff
-if ( which screen &> /dev/null )
+if ( command -v screen &> /dev/null )
 then
   if [[ ${TERM} != screen* ]]
   then
diff --git a/rc.d/startx b/rc.d/startx
index 1a3ad9f..4370d35 100644
--- a/rc.d/startx
+++ b/rc.d/startx
@@ -13,12 +13,12 @@ if [[ -z "${DISPLAY}" && $(id -u) -ge 1000 ]] ; then
             3) VT=vt3 ;;
         esac
 
-        if ( which ck-launch-session &> /dev/null )
+        if ( command -v ck-launch-session &> /dev/null )
         then
             EXEC="exec ck-launch-session"
         fi
 
-        if ( which startx &> /dev/null )
+        if ( command -v startx &> /dev/null )
         then
             ${EXEC} startx 1> ~/.log/xsession-errors 2>&1 -- "${VT}"
         fi