diff --git a/tests/rules/test_upper_to_lower_case.py b/tests/rules/test_upper_to_lower_case.py
index 4d395073..d873c523 100644
--- a/tests/rules/test_upper_to_lower_case.py
+++ b/tests/rules/test_upper_to_lower_case.py
@@ -10,13 +10,6 @@ from thefuck.types import Command
     [
         ("LS", "command not found"),
         ("LS -A", "command not found"),
-        ("CD TESTS", "command not found"),
-        ("CD tests", "command not found"),
-        ("CAT README.MD", "command not found"),
-        ("CAT README.md", "command not found"),
-        ("MV TESTS TESTING", "command not found"),
-        ("GIT ADD .", "command not found"),
-        ("GIT add .", "command not found"),
     ],
 )
 def test_match(script, output):
@@ -39,10 +32,12 @@ def test_not_match(script, output):
 @pytest.mark.parametrize(
     "script, output, new_command",
     [
-        ("LS", "command not found", ["ls"]),
-        ("CD TESTS", "command not found", ["cd tests", "cd TESTS"]),
-        ("CAT README.MD", "command not found", ["cat readme.md", "cat README.MD"]),
-        ("GIT ADD .", "command not found", ["git add ."]),
+        ("LS", "command not found", "ls"),
+        ("CD TESTS", "command not found", "cd tests"),
+        ("CAT README.MD", "command not found", "cat readme.md"),
+        ("GIT ADD .", "command not found", "git add ."),
+        ("GIT ADD .", "command not found", "git add ."),
+        ("MV TESTS TESTING", "command not found", "mv tests testing"),
     ],
 )
 def test_get_new_command(script, output, new_command):
diff --git a/thefuck/rules/upper_to_lower_case.py b/thefuck/rules/upper_to_lower_case.py
index 0080d0a6..5f91b01b 100644
--- a/thefuck/rules/upper_to_lower_case.py
+++ b/thefuck/rules/upper_to_lower_case.py
@@ -1,54 +1,17 @@
-import subprocess
-import itertools
-
-
-def find_all_possible_commands(command):
-    lower_command = command.script.lower().split()
-    upper_command = command.script.upper().split()
-    all_commands = []
-    for i in lower_command:
-        all_commands.append(i)
-    for i in upper_command:
-        all_commands.append(i)
-    permutations = itertools.permutations(all_commands, len(lower_command))
-    new_commands = []
-    for per in permutations:
-        new_command = ""
-        for word in per:
-            new_command += word + " "
-        new_command = new_command.strip()
-        if new_command not in new_commands:
-            new_commands.append(new_command)
-    return new_commands
-
-
-def find_all_correct_commands(new_commands : list):
-    all_correct_commands = []
-    for com in new_commands:
-        result = subprocess.getstatusoutput(com)
-        if result[0] == 0:
-            all_correct_commands.append(com)
-    return all_correct_commands
+from thefuck.utils import get_all_executables, which
 
 
 def match(command):
-    flag = False
-    for i in command.script:
-        if i.isupper():
-            flag = True
-    # checks if the command that typed is valid, if it is not it retunrs false
-    # So if we type: SL -A (instead of LS -A) the rule will not be activated
-    new_commands = find_all_possible_commands(command)
-    all_correct_commands = find_all_correct_commands(new_commands)
-    if len(all_correct_commands) == 0:
-        flag = False
-    return flag
+    return (command.script.isupper()
+    	    and not which(command.script_parts[0])
+            and ('not found' in command.output
+                 or 'is not recognized as' in command.output)
+            and (command.script_parts[0].lower() in get_all_executables()))
 
 
-def get_new_command(command):
-    new_commands = find_all_possible_commands(command)
-    all_correct_commands = find_all_correct_commands(new_commands)
-    return all_correct_commands
+def get_new_command(cmd):
+    return cmd.script.lower()
 
 
-priority = 900
+requires_output = False
+priority = 100
\ No newline at end of file