diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index b4b190f3f9a..62cc262ccb8 100755
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -1647,8 +1647,9 @@ class Helper:
     }
     # Either add symbols to this dictionary or to the symbols dictionary
     # directly: Whichever is easier. They are merged later.
+    _strprefixes = tuple(p + q for p in ('b', 'r', 'u') for q in ("'", '"'))
     _symbols_inverse = {
-        'STRINGS' : ("'", "'''", "r'", "u'", '"""', '"', 'r"', 'u"'),
+        'STRINGS' : ("'", "'''", '"""', '"') + _strprefixes,
         'OPERATORS' : ('+', '-', '*', '**', '/', '//', '%', '<<', '>>', '&',
                        '|', '^', '~', '<', '>', '<=', '>=', '==', '!=', '<>'),
         'COMPARISON' : ('<', '>', '<=', '>=', '==', '!=', '<>'),
@@ -1811,7 +1812,12 @@ has the same effect as typing a particular string at the help> prompt.
                 if not request: break
             except (KeyboardInterrupt, EOFError):
                 break
-            request = strip(replace(request, '"', '', "'", ''))
+            request = strip(request)
+            # Make sure significant trailing quotation marks of literals don't
+            # get deleted while cleaning input
+            if (len(request) > 2 and request[0] == request[-1] in ("'", '"')
+                    and request[0] not in request[1:-1]):
+                request = request[1:-1]
             if lower(request) in ('q', 'quit'): break
             self.help(request)
 
diff --git a/Misc/NEWS.d/next/Library/2018-05-05-09-53-05.bpo-33422.4FtQ0q.rst b/Misc/NEWS.d/next/Library/2018-05-05-09-53-05.bpo-33422.4FtQ0q.rst
new file mode 100644
index 00000000000..0d284d508f1
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-05-05-09-53-05.bpo-33422.4FtQ0q.rst
@@ -0,0 +1,2 @@
+Fix trailing quotation marks getting deleted when looking up byte/string
+literals on pydoc. Patch by Andrés Delfino.