diff --git a/IPython/nbconvert/utils/lexers.py b/IPython/nbconvert/utils/lexers.py
index e8e9290..9506d0a 100644
--- a/IPython/nbconvert/utils/lexers.py
+++ b/IPython/nbconvert/utils/lexers.py
@@ -53,11 +53,8 @@ ipython_tokens = [
   (r'(%)(sx|sc|system)(.*)(\n)', bygroups(Operator, Keyword,
                                        using(BashLexer), Text)),
   (r'(%)(\w+)(.*\n)', bygroups(Operator, Keyword, Text)),
-  (r'^(!)(.+)(\n)', bygroups(Operator, using(BashLexer), Text)),
-  (r'^(.+)(=)(\s*)(!)(.+)(\n)', bygroups(
-      # With the limited syntax allowed on the l.h.s. of a shell capture,
-      # we don't need to differentiate between Python 2 and 3.
-      using(Python3Lexer), Operator, Text, Operator, using(BashLexer), Text)),
+  (r'^(!!)(.+)(\n)', bygroups(Operator, using(BashLexer), Text)),
+  (r'(!)(.+)(\n)', bygroups(Operator, using(BashLexer), Text)),
 ]
 
 def build_ipy_lexer(python3):
diff --git a/IPython/nbconvert/utils/tests/test_lexers.py b/IPython/nbconvert/utils/tests/test_lexers.py
index 2cbc1cc..fa615a9 100644
--- a/IPython/nbconvert/utils/tests/test_lexers.py
+++ b/IPython/nbconvert/utils/tests/test_lexers.py
@@ -34,6 +34,12 @@ class TestLexers(TestsBase):
         ]
         self.assertEqual(tokens, list(self.lexer.get_tokens(fragment)))
 
+        fragment_2 = '!' + fragment
+        tokens_2 = [
+            (Token.Operator, '!!'),
+        ] + tokens[1:]
+        self.assertEqual(tokens_2, list(self.lexer.get_tokens(fragment_2)))
+
         fragment_2 = 'x = ' + fragment
         tokens_2 = [
             (Token.Name, 'x'),