diff --git a/src/callbacks.py b/src/callbacks.py
index 9bd22a355..5ec7dbb77 100644
--- a/src/callbacks.py
+++ b/src/callbacks.py
@@ -244,6 +244,7 @@ class Tokenizer:
 
     def _insideBrackets(self, lexer):
         ret = []
+        firstToken = True
         while True:
             token = lexer.get_token()
             if not token:
@@ -255,9 +256,15 @@ class Tokenizer:
             elif token == self.right:
                 return ret
             elif token == self.left:
+                if firstToken:
+                    s = 'The command called may not be the result ' \
+                        'of a nested command.'
+                    raise SyntaxError, 'The command called may not be the ' \
+                                       'result or a nested command.'
                 ret.append(self._insideBrackets(lexer))
             else:
                 ret.append(self._handleToken(token))
+            firstToken = False
         return ret
 
     def tokenize(self, s):
diff --git a/test/test_callbacks.py b/test/test_callbacks.py
index 5e4872572..4bfdd1043 100644
--- a/test/test_callbacks.py
+++ b/test/test_callbacks.py
@@ -94,6 +94,7 @@ class TokenizerTestCase(SupyTestCase):
     def testError(self):
         self.assertRaises(SyntaxError, tokenize, '[foo') #]
         self.assertRaises(SyntaxError, tokenize, '"foo') #"
+        self.assertRaises(SyntaxError, tokenize, '[[foo]]')
 
     def testPipe(self):
         try: