diff --git a/lark/lexer.py b/lark/lexer.py
index 3dabd95..6fb6572 100644
--- a/lark/lexer.py
+++ b/lark/lexer.py
@@ -9,7 +9,7 @@ class LexError(Exception):
     pass
 
 class UnexpectedInput(LexError):
-    def __init__(self, seq, lex_pos, line, column):
+    def __init__(self, seq, lex_pos, line, column, allowed=None):
         context = seq[lex_pos:lex_pos+5]
         message = "No token defined for: '%s' in %r at line %d" % (seq[lex_pos], context, line)
 
@@ -18,6 +18,7 @@ class UnexpectedInput(LexError):
         self.line = line
         self.column = column
         self.context = context
+        self.allowed = allowed
 
 class Token(Str):
     def __new__(cls, type_, value, pos_in_stream=None, line=None, column=None):
@@ -238,7 +239,6 @@ class ContextualLexer:
                     break
             else:
                 if lex_pos < len(stream):
-                    print("Allowed tokens:", lexer.tokens)
-                    raise UnexpectedInput(stream, lex_pos, line, lex_pos - col_start_pos)
+                    raise UnexpectedInput(stream, lex_pos, line, lex_pos - col_start_pos, lexer.tokens)
                 break
 
diff --git a/lark/load_grammar.py b/lark/load_grammar.py
index 9bf6f95..8762176 100644
--- a/lark/load_grammar.py
+++ b/lark/load_grammar.py
@@ -290,6 +290,31 @@ class ExtractAnonTokens(InlineTransformer):
 def _rfind(s, choices):
     return max(s.rfind(c) for c in choices)
 
+
+
+def _fix_escaping(s):
+    s = s.replace('\\"', '"')
+    w = ''
+    i = iter(s)
+    for n in i:
+        w += n
+        if n == '\\':
+            n2 = next(i)
+            if n2 == '\\':
+                w += '\\\\'
+            elif n2 not in 'unftr':
+                w += '\\'
+            w += n2
+
+    to_eval = "u'''%s'''" % w
+    try:
+        s = literal_eval(to_eval)
+    except SyntaxError as e:
+        raise ValueError(v, e)
+
+    return s
+
+
 def _literal_to_pattern(literal):
     v = literal.value
     flag_start = _rfind(v, '/"')+1
@@ -300,13 +325,12 @@ def _literal_to_pattern(literal):
     v = v[:flag_start]
     assert v[0] == v[-1] and v[0] in '"/'
     x = v[1:-1]
-    x = re.sub(r'(\\[wd/ .]|\\\[|\\\])', r'\\\1', x)
-    x = x.replace("'", r"\'")
-    to_eval = "u'''%s'''" % x
-    try:
-        s = literal_eval(to_eval)
-    except SyntaxError as e:
-        raise ValueError(v, e)
+
+    s = _fix_escaping(x)
+
+    if v[0] == '"':
+        s = s.replace('\\\\', '\\')
+
     return { 'STRING': PatternStr,
              'REGEXP': PatternRE }[literal.type](s, flags or None)
 
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 33b9e5e..35c1a44 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -19,7 +19,7 @@ logging.basicConfig(level=logging.INFO)
 
 from lark.lark import Lark
 from lark.common import GrammarError, ParseError
-from lark.lexer import LexError
+from lark.lexer import LexError, UnexpectedInput
 from lark.tree import Tree, Transformer
 
 __path__ = os.path.dirname(__file__)
@@ -673,7 +673,7 @@ def _make_parser_test(LEXER, PARSER):
                       """)
             x = g.parse(r'\a')
 
-            g = _Lark(r"""start: /\\\\/ /a/
+            g = _Lark(r"""start: /\\/ /a/
                       """)
             x = g.parse(r'\a')
 
@@ -961,6 +961,49 @@ def _make_parser_test(LEXER, PARSER):
             self.assertEqual(tree.children, ['1'])
 
 
+        @unittest.skipIf(LEXER==None, "Scanless doesn't support regular expressions")
+        def test_regex_escaping(self):
+            expected_error = ParseError if LEXER == 'dynamic' else UnexpectedInput
+            # TODO Make dynamic parser raise UnexpectedInput if nothing scans?
+
+            g = _Lark("start: /[ab]/")
+            g.parse('a')
+            g.parse('b')
+
+            self.assertRaises( expected_error, g.parse, 'c')
+
+            _Lark(r'start: /\w/').parse('a')
+
+            g = _Lark(r'start: /\\w/')
+            self.assertRaises( expected_error, g.parse, 'a')
+            g.parse(r'\w')
+
+            _Lark(r'start: /\[/').parse('[')
+
+            _Lark(r'start: /\//').parse('/')
+
+            _Lark(r'start: /\\/').parse('\\')
+
+            _Lark(r'start: /\[ab]/').parse('[ab]')
+
+            _Lark(r'start: /\\[ab]/').parse('\\a')
+
+            _Lark(r'start: /\t/').parse('\t')
+
+            _Lark(r'start: /\\t/').parse('\\t')
+
+            _Lark(r'start: /\\\t/').parse('\\\t')
+
+            _Lark(r'start: "\t"').parse('\t')
+
+            _Lark(r'start: "\\t"').parse('\\t')
+
+            _Lark(r'start: "\\\t"').parse('\\\t')
+
+
+
+
+
 
     _NAME = "Test" + PARSER.capitalize() + (LEXER or 'Scanless').capitalize()
     _TestParser.__name__ = _NAME