I had to patch bash-completion, otherwise doing "<tab><tab>" on an empty line gave:
bash: words: bad array subscript

bash-completion-2.1-5.fc21.noarch

--- bash_completion	2014-10-28 13:48:35.677151105 +0100
+++ bash_completion	2014-10-28 13:48:25.442061258 +0100
@@ -694,6 +694,8 @@
         return 1
     fi
 
+    [[ $words ]] || return 0
+
     # Remove all redirections so completions don't have to deal with them.
     local i skip
     for (( i=1; i < ${#words[@]}; )); do