diff --git a/mpf/core/utility_functions.py b/mpf/core/utility_functions.py
index 74421ae1a..3e4d8fb89 100644
--- a/mpf/core/utility_functions.py
+++ b/mpf/core/utility_functions.py
@@ -802,11 +802,12 @@ def set_bit(hex_string, bit):
             bit (_type_): Bit to set, e.g. 3
 
         Returns:
-            _type_: Returns the hex string with the bit set, e.g. '89'
+            _type_: Returns the hex string with the bit set, e.g. '89'.
+            The return string will be the same length as the input string.
         """
         num = int(hex_string, 16)
         num |= 1 << bit
-        return Util.int_to_hex_string(num)
+        return Util.int_to_hex_string(num).zfill(len(hex_string))
 
     @staticmethod
     def clear_bit(hex_string, bit):
diff --git a/mpf/tests/test_Utility_Functions.py b/mpf/tests/test_Utility_Functions.py
index 0039cde04..533cbd78b 100644
--- a/mpf/tests/test_Utility_Functions.py
+++ b/mpf/tests/test_Utility_Functions.py
@@ -215,3 +215,11 @@ def test_power_of_2(self):
         self.assertTrue(Util.is_power2(256))
         self.assertFalse(Util.is_power2(3))
         self.assertFalse(Util.is_power2(222))
+
+    def test_bit_functions(self):
+        self.assertEqual(Util.set_bit('00', 0), '01')
+        self.assertEqual(Util.set_bit('02', 2), '06')
+        self.assertEqual(Util.clear_bit('91', 4), '81')
+        self.assertEqual(Util.clear_bit('81', 3), '81')  # no change
+        self.assertEqual(Util.check_bit('01', 0), True)
+        self.assertEqual(Util.check_bit('91', 5), False)