diff --git a/modules/python/init.zsh b/modules/python/init.zsh
index fa9175e..5715b02 100644
--- a/modules/python/init.zsh
+++ b/modules/python/init.zsh
@@ -16,9 +16,12 @@ elif (( $+commands[pyenv] )); then
   eval "$(pyenv init -)"
 
 # Prepend PEP 370 per user site packages directory, which defaults to
-# ~/Library/Python on Mac OS X and ~/.local elsewhere, to PATH.
+# ~/Library/Python on Mac OS X and ~/.local elsewhere, to PATH. The
+# path can be overridden using PYTHONUSERBASE.
 else
-  if [[ "$OSTYPE" == darwin* ]]; then
+  if [[ -n "$PYTHONUSERBASE" ]]; then
+    path=($PYTHONUSERBASE/bin $path)
+  elif [[ "$OSTYPE" == darwin* ]]; then
     path=($HOME/Library/Python/*/bin(N) $path)
   else
     # This is subject to change.
diff --git a/modules/tmux/init.zsh b/modules/tmux/init.zsh
index c6c3626..29b547f 100644
--- a/modules/tmux/init.zsh
+++ b/modules/tmux/init.zsh
@@ -21,12 +21,12 @@ if [[ -z "$TMUX" && -z "$EMACS" && -z "$VIM" ]] && ( \
   ( [[ -n "$SSH_TTY" ]] && zstyle -t ':prezto:module:tmux:auto-start' remote ) ||
   ( [[ -z "$SSH_TTY" ]] && zstyle -t ':prezto:module:tmux:auto-start' local ) \
 ); then
-  tmux_session='prezto'
+  tmux start-server
 
-  # Create a first 'prezto' session if tmux is starting.
+  # Create a 'prezto' session if no session has been defined in tmux.conf.
   if ! tmux has-session 2> /dev/null; then
+    tmux_session='prezto'
     tmux \
-      start-server \; \
       new-session -d -s "$tmux_session" \; \
       set-option -t "$tmux_session" destroy-unattached off &> /dev/null
   fi