diff --git a/core/cmd.py b/core/cmd.py
index a7d04d5..4cc2963 100644
--- a/core/cmd.py
+++ b/core/cmd.py
@@ -30,7 +30,7 @@ class Command:
 	'''
 	A shell command with argument substitution and output capture.
 	
-	>>> c = Command(['process.sh', '-x', 'ARGUMENT'])
+	>>> c = Command('process.sh', '-x', 'ARGUMENT')
 	>>> c.ARGUMENT = 'file.txt'
 	>>> c.dump()
 	['process.sh', '-x', 'file.txt']
@@ -58,8 +58,8 @@ class Command:
 				self.sequence[i] = value
 				found = True
 		
-		#if not found:
-			#raise AttributeError('Command has no attribute \'%s\'' %(name))
+		if not found:
+			raise AttributeError('Command has no attribute \'%s\'' %(name))
 	
 	def reset(self):
 		self.__dict__['sequence'] = list(self.sequence_original)