diff --git a/README.md b/README.md
index 5c5e932..86f6e12 100644
--- a/README.md
+++ b/README.md
@@ -16,23 +16,28 @@ non-standard core utilities.
 
         zsh
 
-  2. Clone the repository:
+  2. Set the path to the Prezto installation directory:
 
-        git clone --recursive https://github.com/sorin-ionescu/prezto.git "${ZDOTDIR:-$HOME}/.zprezto"
+      ZDOTDIR="${ZDOTDIR:-$HOME}"
+      PREZTO="$ZDOTDIR/.zprezto"
 
-  3. Create a new Zsh configuration by copying the Zsh configuration files
+  3. Clone the repository:
+
+        git clone --recursive https://github.com/sorin-ionescu/prezto.git "$PREZTO"
+
+  4. Create a new Zsh configuration by copying the Zsh configuration files
      provided:
 
         setopt EXTENDED_GLOB
-        for rcfile in "${ZDOTDIR:-$HOME}"/.zprezto/runcoms/^README.md(.N); do
-          ln -s "$rcfile" "${ZDOTDIR:-$HOME}/.${rcfile:t}"
+        for rcfile in "$PREZTO/runcoms/^README.md(.N); do
+          ln -s "$rcfile" "${ZDOTDIR}/.${rcfile:t}"
         done
 
-  4. Set Zsh as your default shell:
+  5. Set Zsh as your default shell:
 
         chsh -s /bin/zsh
 
-  5. Open a new Zsh terminal window or tab.
+  6. Open a new Zsh terminal window or tab.
 
 ### Troubleshooting
 
diff --git a/init.zsh b/init.zsh
index fde7bcd..d55ea5f 100644
--- a/init.zsh
+++ b/init.zsh
@@ -31,7 +31,7 @@ function pmodload {
   pmodules=("$argv[@]")
 
   # Add functions to $fpath.
-  fpath=(${pmodules:+${ZDOTDIR:-$HOME}/.zprezto/modules/${^pmodules}/functions(/FN)} $fpath)
+  fpath=(${pmodules:+$PREZTO/modules/${^pmodules}/functions(/FN)} $fpath)
 
   function {
     local pfunction
@@ -40,7 +40,7 @@ function pmodload {
     setopt LOCAL_OPTIONS EXTENDED_GLOB
 
     # Load Prezto functions.
-    for pfunction in ${ZDOTDIR:-$HOME}/.zprezto/modules/${^pmodules}/functions/$~pfunction_glob; do
+    for pfunction in $PREZTO/modules/${^pmodules}/functions/$~pfunction_glob; do
       autoload -Uz "$pfunction"
     done
   }
@@ -49,19 +49,19 @@ function pmodload {
   for pmodule in "$pmodules[@]"; do
     if zstyle -t ":prezto:module:$pmodule" loaded 'yes' 'no'; then
       continue
-    elif [[ ! -d "${ZDOTDIR:-$HOME}/.zprezto/modules/$pmodule" ]]; then
+    elif [[ ! -d "$PREZTO/modules/$pmodule" ]]; then
       print "$0: no such module: $pmodule" >&2
       continue
     else
-      if [[ -s "${ZDOTDIR:-$HOME}/.zprezto/modules/$pmodule/init.zsh" ]]; then
-        source "${ZDOTDIR:-$HOME}/.zprezto/modules/$pmodule/init.zsh"
+      if [[ -s "$PREZTO/modules/$pmodule/init.zsh" ]]; then
+        source "$PREZTO/modules/$pmodule/init.zsh"
       fi
 
       if (( $? == 0 )); then
         zstyle ":prezto:module:$pmodule" loaded 'yes'
       else
         # Remove the $fpath entry.
-        fpath[(r)${ZDOTDIR:-$HOME}/.zprezto/modules/${pmodule}/functions]=()
+        fpath[(r)$PREZTO/modules/${pmodule}/functions]=()
 
         function {
           local pfunction
@@ -71,7 +71,7 @@ function pmodload {
           setopt LOCAL_OPTIONS EXTENDED_GLOB
 
           # Unload Prezto functions.
-          for pfunction in ${ZDOTDIR:-$HOME}/.zprezto/modules/$pmodule/functions/$~pfunction_glob; do
+          for pfunction in $PREZTO/modules/$pmodule/functions/$~pfunction_glob; do
             unfunction "$pfunction"
           done
         }
@@ -87,8 +87,8 @@ function pmodload {
 #
 
 # Source the Prezto configuration file.
-if [[ -s "${ZDOTDIR:-$HOME}/.zpreztorc" ]]; then
-  source "${ZDOTDIR:-$HOME}/.zpreztorc"
+if [[ -s "$ZDOTDIR/.zpreztorc" ]]; then
+  source "$ZDOTDIR/.zpreztorc"
 fi
 
 # Disable color and theme in dumb terminals.
diff --git a/modules/completion/init.zsh b/modules/completion/init.zsh
index 3ffad63..0721896 100644
--- a/modules/completion/init.zsh
+++ b/modules/completion/init.zsh
@@ -36,7 +36,7 @@ unsetopt FLOW_CONTROL      # Disable start/stop characters in shell editor.
 
 # Use caching to make completion for cammands such as dpkg and apt usable.
 zstyle ':completion::complete:*' use-cache on
-zstyle ':completion::complete:*' cache-path "${ZDOTDIR:-$HOME}/.zcompcache"
+zstyle ':completion::complete:*' cache-path "$ZDOTDIR/.zcompcache"
 
 # Case-insensitive (all), partial-word, and then substring completion.
 if zstyle -t ':prezto:module:completion:*' case-sensitive; then
diff --git a/modules/history/init.zsh b/modules/history/init.zsh
index 31db4c5..54c27c3 100644
--- a/modules/history/init.zsh
+++ b/modules/history/init.zsh
@@ -10,7 +10,7 @@
 # Variables
 #
 
-HISTFILE="${ZDOTDIR:-$HOME}/.zhistory"       # The path to the history file.
+HISTFILE="$ZDOTDIR/.zhistory"    # The path to the history file.
 HISTSIZE=10000                   # The maximum number of events to save in the internal history.
 SAVEHIST=10000                   # The maximum number of events to save in the history file.
 
diff --git a/runcoms/zlogin b/runcoms/zlogin
index 32f28cf..074aaf9 100644
--- a/runcoms/zlogin
+++ b/runcoms/zlogin
@@ -8,7 +8,7 @@
 # Execute code that does not affect the current session in the background.
 {
   # Compile the completion dump to increase startup speed.
-  zcompdump="${ZDOTDIR:-$HOME}/.zcompdump"
+  zcompdump="$ZDOTDIR/.zcompdump"
   if [[ -s "$zcompdump" && (! -s "${zcompdump}.zwc" || "$zcompdump" -nt "${zcompdump}.zwc") ]]; then
     zcompile "$zcompdump"
   fi
diff --git a/runcoms/zshenv b/runcoms/zshenv
index 7b12120..3c00b44 100644
--- a/runcoms/zshenv
+++ b/runcoms/zshenv
@@ -10,3 +10,10 @@ if [[ "$SHLVL" -eq 1 && ! -o LOGIN ]]; then
   source "${ZDOTDIR:-$HOME}/.zprofile"
 fi
 
+#
+# Zsh
+#
+
+ZDOTDIR="${ZDOTDIR:-$HOME}"
+PREZTO="$ZDOTDIR/.zprezto"
+
diff --git a/runcoms/zshrc b/runcoms/zshrc
index e87283f..5c6b02d 100644
--- a/runcoms/zshrc
+++ b/runcoms/zshrc
@@ -6,8 +6,8 @@
 #
 
 # Source Prezto.
-if [[ -s "${ZDOTDIR:-$HOME}/.zprezto/init.zsh" ]]; then
-  source "${ZDOTDIR:-$HOME}/.zprezto/init.zsh"
+if [[ -s "$PREZTO/init.zsh" ]]; then
+  source "$PREZTO/init.zsh"
 fi
 
 # Customize to your needs...