diff --git a/thefuck/utils.py b/thefuck/utils.py
index f6c0bb71..2bb20a22 100644
--- a/thefuck/utils.py
+++ b/thefuck/utils.py
@@ -264,7 +264,7 @@ def get_valid_history_without_current(command):
     from thefuck.shells import shell
     history = shell.get_history()
     tf_alias = get_alias()
-    executables = get_all_executables()
+    executables = set(get_all_executables())
     return [line for line in _not_corrected(history, tf_alias)
             if not line.startswith(tf_alias) and not line == command.script
             and line.split(' ')[0] in executables]