2 files changed, 7 insertions, 1 deletions
diff --git a/Lib/sre_parse.py b/Lib/sre_parse.py
index 9aea56a..19dd4fc 100644
--- a/Lib/sre_parse.py
+++ b/Lib/sre_parse.py
@@ -235,7 +235,7 @@ def _class_escape(source, escape):
     if code:
         return code
     code = CATEGORIES.get(escape)
-    if code:
+    if code and code[0] == IN:
         return code
     try:
         c = escape[1:2]
diff --git a/Lib/test/test_re.py b/Lib/test/test_re.py
index 0c8c676..6b047e4 100644
--- a/Lib/test/test_re.py
+++ b/Lib/test/test_re.py
@@ -857,6 +857,12 @@ class ReTests(unittest.TestCase):
         # Test behaviour when not given a string or pattern as parameter
         self.assertRaises(TypeError, re.compile, 0)
 
+    def test_bug_13899(self):
+        # Issue #13899: re pattern r"[\A]" should work like "A" but matches
+        # nothing. Ditto B and Z.
+        self.assertEqual(re.findall(r'[\A\B\b\C\Z]', 'AB\bCZ'),
+                         ['A', 'B', '\b', 'C', 'Z'])
+
     @bigmemtest(size=_2G, memuse=character_size)
     def test_large_search(self, size):
         # Issue #10182: indices were 32-bit-truncated.