diff --git a/share/completions/functions.fish b/share/completions/functions.fish
index c25e9777e..6010f583a 100644
--- a/share/completions/functions.fish
+++ b/share/completions/functions.fish
@@ -1,4 +1,13 @@
-complete -c functions -s e -l erase -d "Erase function" -x -a "(functions -n)"
+function __fish_maybe_list_all_functions
+	# if the current commandline token starts with an _, list all functions
+	if string match -qr -- '^_' (commandline -ct)
+		functions -an
+	else
+		functions -n
+	end
+end
+
+complete -c functions -s e -l erase -d "Erase function" -x -a "(__fish_maybe_list_all_functions)"
 complete -c functions -xa "(functions -na)" -d "Function"
 complete -c functions -s a -l all -d "Show hidden functions"
 complete -c functions -s h -l help -d "Display help and exit"