diff --git a/src/Symfony/Component/ExpressionLanguage/Lexer.php b/src/Symfony/Component/ExpressionLanguage/Lexer.php
index 48b15ffe7c23..01ca29301836 100644
--- a/src/Symfony/Component/ExpressionLanguage/Lexer.php
+++ b/src/Symfony/Component/ExpressionLanguage/Lexer.php
@@ -73,7 +73,7 @@ public function tokenize($expression)
                 // strings
                 $tokens[] = new Token(Token::STRING_TYPE, stripcslashes(substr($match[0], 1, -1)), $cursor + 1);
                 $cursor += \strlen($match[0]);
-            } elseif (preg_match('/not in(?=[\s(])|\!\=\=|not(?=[\s(])|and(?=[\s(])|\=\=\=|\>\=|or(?=[\s(])|\<\=|\*\*|\.\.|in(?=[\s(])|&&|\|\||matches|\=\=|\!\=|\*|~|%|\/|\>|\||\!|\^|&|\+|\<|\-/A', $expression, $match, 0, $cursor)) {
+            } elseif (preg_match('/(?<=^|[\s(])not in(?=[\s(])|\!\=\=|(?<=^|[\s(])not(?=[\s(])|(?<=^|[\s(])and(?=[\s(])|\=\=\=|\>\=|(?<=^|[\s(])or(?=[\s(])|\<\=|\*\*|\.\.|(?<=^|[\s(])in(?=[\s(])|&&|\|\||(?<=^|[\s(])matches|\=\=|\!\=|\*|~|%|\/|\>|\||\!|\^|&|\+|\<|\-/A', $expression, $match, 0, $cursor)) {
                 // operators
                 $tokens[] = new Token(Token::OPERATOR_TYPE, $match[0], $cursor + 1);
                 $cursor += \strlen($match[0]);
diff --git a/src/Symfony/Component/ExpressionLanguage/Resources/bin/generate_operator_regex.php b/src/Symfony/Component/ExpressionLanguage/Resources/bin/generate_operator_regex.php
index e1196c7f514a..c86e96252618 100644
--- a/src/Symfony/Component/ExpressionLanguage/Resources/bin/generate_operator_regex.php
+++ b/src/Symfony/Component/ExpressionLanguage/Resources/bin/generate_operator_regex.php
@@ -15,9 +15,13 @@
 
 $regex = [];
 foreach ($operators as $operator => $length) {
-    // an operator that ends with a character must be followed by
-    // a whitespace or a parenthesis
-    $regex[] = preg_quote($operator, '/').(ctype_alpha($operator[$length - 1]) ? '(?=[\s(])' : '');
+    // Collisions of character operators:
+    // - an operator that begins with a character must have a space or a parenthesis before or starting at the beginning of a string
+    // - an operator that ends with a character must be followed by a whitespace or a parenthesis
+    $regex[] =
+        (ctype_alpha($operator[0]) ? '(?<=^|[\s(])' : '')
+        .preg_quote($operator, '/')
+        .(ctype_alpha($operator[$length - 1]) ? '(?=[\s(])' : '');
 }
 
 echo '/'.implode('|', $regex).'/A';
diff --git a/src/Symfony/Component/ExpressionLanguage/Tests/ExpressionLanguageTest.php b/src/Symfony/Component/ExpressionLanguage/Tests/ExpressionLanguageTest.php
index f69ee57982e8..fc2f80e17b3a 100644
--- a/src/Symfony/Component/ExpressionLanguage/Tests/ExpressionLanguageTest.php
+++ b/src/Symfony/Component/ExpressionLanguage/Tests/ExpressionLanguageTest.php
@@ -233,6 +233,17 @@ public function testCachingWithDifferentNamesOrder()
         $expressionLanguage->compile($expression, ['B' => 'b', 'a']);
     }
 
+    public function testOperatorCollisions()
+    {
+        $expressionLanguage = new ExpressionLanguage();
+        $expression = 'foo.not in [bar]';
+        $compiled = $expressionLanguage->compile($expression, ['foo', 'bar']);
+        $this->assertSame('in_array($foo->not, [0 => $bar])', $compiled);
+
+        $result = $expressionLanguage->evaluate($expression, ['foo' => (object) ['not' => 'test'], 'bar' => 'test']);
+        $this->assertTrue($result);
+    }
+
     /**
      * @dataProvider getRegisterCallbacks
      */
diff --git a/src/Symfony/Component/ExpressionLanguage/Tests/LexerTest.php b/src/Symfony/Component/ExpressionLanguage/Tests/LexerTest.php
index 9ab6b1e843ce..6c3d1a7d2519 100644
--- a/src/Symfony/Component/ExpressionLanguage/Tests/LexerTest.php
+++ b/src/Symfony/Component/ExpressionLanguage/Tests/LexerTest.php
@@ -112,6 +112,18 @@ public function getTokenizeData()
                 [new Token('string', '#foo', 1)],
                 '"#foo"',
             ],
+            [
+                [
+                    new Token('name', 'foo', 1),
+                    new Token('punctuation', '.', 4),
+                    new Token('name', 'not', 5),
+                    new Token('operator', 'in', 9),
+                    new Token('punctuation', '[', 12),
+                    new Token('name', 'bar', 13),
+                    new Token('punctuation', ']', 16),
+                ],
+                'foo.not in [bar]',
+            ],
         ];
     }
 }
diff --git a/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php b/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php
index 84b30dc151cf..2d5a0a6c8c81 100644
--- a/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php
+++ b/src/Symfony/Component/ExpressionLanguage/Tests/ParserTest.php
@@ -53,6 +53,9 @@ public function getParseData()
         $arguments->addElement(new Node\ConstantNode(2));
         $arguments->addElement(new Node\ConstantNode(true));
 
+        $arrayNode = new Node\ArrayNode();
+        $arrayNode->addElement(new Node\NameNode('bar'));
+
         return [
             [
                 new Node\NameNode('a'),
@@ -151,6 +154,36 @@ public function getParseData()
                 'bar',
                 ['foo' => 'bar'],
             ],
+
+            // Operators collisions
+            [
+                new Node\BinaryNode(
+                    'in',
+                    new Node\GetAttrNode(
+                        new Node\NameNode('foo'),
+                        new Node\ConstantNode('not', true),
+                        new Node\ArgumentsNode(),
+                        Node\GetAttrNode::PROPERTY_CALL
+                    ),
+                    $arrayNode
+                ),
+                'foo.not in [bar]',
+                ['foo', 'bar'],
+            ],
+            [
+                new Node\BinaryNode(
+                    'or',
+                    new Node\UnaryNode('not', new Node\NameNode('foo')),
+                    new Node\GetAttrNode(
+                        new Node\NameNode('foo'),
+                        new Node\ConstantNode('not', true),
+                        new Node\ArgumentsNode(),
+                        Node\GetAttrNode::PROPERTY_CALL
+                    )
+                ),
+                'not foo or foo.not',
+                ['foo'],
+            ],
         ];
     }