diff --git a/prompt_fresh_setup b/prompt_fresh_setup
index 7e03286..04c9b47 100644
--- a/prompt_fresh_setup
+++ b/prompt_fresh_setup
@@ -110,7 +110,9 @@ fresh_line_one() {
   fi
 
   # Unset vim/tmux navigate flag to handle C-z and multiple vim jobs.
-  tmux set-window-option -u @vim$TMUX_PANE
+  if [[ ! -z "$TMUX" ]]; then
+    tmux set-window-option -u @vim$TMUX_PANE
+  fi
 
   # If a virtualenv is enabled, display it's basename
   if [[ ! -z "$VIRTUAL_ENV" ]]; then