diff --git a/driver/tef.py b/driver/tef.py
index ad8308a..a411f72 100644
--- a/driver/tef.py
+++ b/driver/tef.py
@@ -107,10 +107,10 @@ class TEF6686(BaseTEF668X):
 
     @_command_wrapper
     def FM_Set_LevelStep(self, step1: int = -20, step2: int = -30, step3: int = -40, step4: int = -50, step5: int = -60, step6: int = -60, step7: int = -60):
-        return b"\x20\x26\x01" + pack(step1, step2, step3, step4, step5, step6, step7), None, None
+        return b"\x20\x26\x01" + pack(SignedInt(step1), SignedInt(step2), SignedInt(step3), SignedInt(step4), SignedInt(step5), SignedInt(step6), SignedInt(step7)), None, None
     @_command_wrapper
     def AM_Set_LevelStep(self, step1: int = -10, step2: int = -20, step3: int = -30, step4: int = -40, step5: int = -50, step6: int = -60, step7: int = -60):
-        return b"\x21\x26\x01" + pack(step1, step2, step3, step4, step5, step6, step7), None, None
+        return b"\x21\x26\x01" + pack(SignedInt(step1), SignedInt(step2), SignedInt(step3), SignedInt(step4), SignedInt(step5), SignedInt(step6), SignedInt(step7)), None, None
 
     @_command_wrapper
     def FM_Set_LevelOffset(self, offset: int = 0): return b"\x20\x27\x01" + pack(SignedInt(offset)), None, None