minor fix
diff --git a/Mac/Lib/toolbox/aetools.py b/Mac/Lib/toolbox/aetools.py
index 565cdec..53d2cbd 100644
--- a/Mac/Lib/toolbox/aetools.py
+++ b/Mac/Lib/toolbox/aetools.py
@@ -125,7 +125,7 @@
 			self.target = signature
 		elif type(signature) == InstanceType and hasattr(signature, '__aepack__'):
 			self.target = signature.__aepack__()
-		elif type(signature) == StringType and len(signature) != 4:
+		elif type(signature) == StringType and len(signature) == 4:
 			self.target = AE.AECreateDesc(AppleEvents.typeApplSignature, signature)
 		else:
 			raise TypeError, "signature should be 4-char string or AEDesc"