diff --git a/autoload/tmux.vim b/autoload/tmux.vim
new file mode 100644
index 0000000..910259e
--- /dev/null
+++ b/autoload/tmux.vim
@@ -0,0 +1,9 @@
+let s:tmux_option = '@vim'.substitute($TMUX_PANE, '%', '\\%', 'g')
+
+function! tmux#setNavigationFlag() abort
+  call system('tmux set-window-option '.s:tmux_option.' 1')
+endfunction
+
+function! tmux#unsetNavigationFlag() abort
+  call system('tmux set-window-option -u '.s:tmux_option)
+endfunction
diff --git a/plugin/autocmds.vim b/plugin/autocmds.vim
index 9f11c68..936af35 100644
--- a/plugin/autocmds.vim
+++ b/plugin/autocmds.vim
@@ -2,10 +2,10 @@ augroup benieAugroup
   autocmd!
 
   if $TMUX !=# ''
-    " Set tmux window option to detect when to change pane.
-    let s:tmux_option = '@vim'.substitute($TMUX_PANE, '%', '\\%', 'g')
-    call system('tmux set-window-option '.s:tmux_option.' 1')
-    au VimLeave * call system('tmux set-window-option -u '.s:tmux_option)
+    " [Un]set tmux window option to detect when to change pane.
+    call tmux#setNavigationFlag()
+    au FocusGained * call tmux#setNavigationFlag()
+    au VimLeave * call tmux#unsetNavigationFlag()
   endif
 
   " Reopening a file at last curson position