diff --git a/parso/python/normalizer.py b/parso/python/normalizer.py
index b081aeb..00372a0 100644
--- a/parso/python/normalizer.py
+++ b/parso/python/normalizer.py
@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+import codecs
 from contextlib import contextmanager
 
 from parso.normalizer import Normalizer, NormalizerConfig, Issue
@@ -514,22 +515,40 @@ class ErrorFinder(Normalizer):
                 self._add_syntax_error('invalid syntax', leaf)
         elif leaf.type == 'name':
             if leaf.value == '__debug__' and leaf.is_definition():
-                if self._version <= (2, 7):
+                if self._version < (3, 0):
                     message = 'cannot assign to __debug__'
                 else:
                     message = 'assignment to keyword'
                 self._add_syntax_error(message, leaf)
-            if leaf.value == 'None' and self._version <= (2, 7) and leaf.is_definition():
+            if leaf.value == 'None' and self._version < (3, 0) and leaf.is_definition():
                 self._add_syntax_error('cannot assign to None', leaf)
 
             self._context.add_name(leaf)
         elif leaf.type == 'string':
-            if 'b' in leaf.string_prefix.lower() \
+            string_prefix = leaf.string_prefix.lower()
+            if 'b' in string_prefix \
                     and any(c for c in leaf.value if ord(c) > 127):
                 # TODO add check for python 3
                 # b'ä'
                 message = "bytes can only contain ASCII literal characters."
                 self._add_syntax_error(message, leaf)
+
+            if 'r' not in string_prefix:
+                # Raw strings don't need to be checked if they have proper
+                # escaping.
+                is_bytes = self._version < (3, 0)
+                if 'b' in string_prefix:
+                    is_bytes = True
+                if 'u' in string_prefix:
+                    is_bytes = False
+                func = codecs.escape_decode if is_bytes else codecs.unicode_escape_decode
+                try:
+                    func(leaf._get_payload())
+                except UnicodeDecodeError as e:
+                    self._add_syntax_error('(unicode error) ' + str(e), leaf)
+                except ValueError as e:
+                    self._add_syntax_error('(value error) ' + str(e), leaf)
+
         elif leaf.value == 'continue':
             in_loop = False
             for block in self._context.blocks:
diff --git a/parso/python/tree.py b/parso/python/tree.py
index 46ec8cd..c93af25 100644
--- a/parso/python/tree.py
+++ b/parso/python/tree.py
@@ -214,6 +214,14 @@ class String(Literal):
     def string_prefix(self):
         return re.match('\w*(?=[\'"])', self.value).group(0)
 
+    def _get_payload(self):
+        match = re.search(
+            r'''('{3}|"{3}|'|")(.*)$''',
+            self.value,
+            flags=re.DOTALL
+        )
+        return match.group(2)[:-len(match.group(1))]
+
 
 class _StringComparisonMixin(object):
     def __eq__(self, other):
diff --git a/test/normalizer_issue_files/allowed_syntax.py b/test/normalizer_issue_files/allowed_syntax.py
index 2a7346e..237b818 100644
--- a/test/normalizer_issue_files/allowed_syntax.py
+++ b/test/normalizer_issue_files/allowed_syntax.py
@@ -39,3 +39,8 @@ except:
     pass
 except ZeroDivisionError:
     pass
+
+
+r'\n'
+r'\x'
+b'\n'
diff --git a/test/test_python_errors.py b/test/test_python_errors.py
index 4e1328c..2d41faf 100644
--- a/test/test_python_errors.py
+++ b/test/test_python_errors.py
@@ -95,6 +95,16 @@ FAILING_EXAMPLES = [
     '(x for 1 in y)',
     '{x for 1 in y}',
     '{x:x for 1 in y}',
+    # Unicode/Bytes issues.
+    r'u"\x"',
+    r'u"\"',
+    r'u"\u"',
+    r'u"""\U"""',
+    r'u"\Uffffffff"',
+    r"u'''\N{}'''",
+    r"u'\N{foo}'",
+    r'b"\x"',
+    r'b"\"',
 
     # SyntaxErrors from Python/symtable.c
     'def f(x, x): pass',
@@ -304,6 +314,10 @@ def _get_actual_exception(code):
     if sys.version_info[:2] == (2, 6) and wanted == 'SyntaxError: unexpected EOF while parsing':
         wanted = 'SyntaxError: invalid syntax'
 
+    if wanted == 'SyntaxError: EOL while scanning string literal':
+        # TODO This is not what we want in the future. Remove this.
+        wanted = 'SyntaxError: invalid syntax'
+
     if wanted == 'SyntaxError: non-keyword arg after keyword arg':
         # The python 3.5+ way, a bit nicer.
         wanted = 'SyntaxError: positional argument follows keyword argument'