diff --git a/pre_commit_hooks/trailing_whitespace_fixer.py b/pre_commit_hooks/trailing_whitespace_fixer.py
index 0642ac0..c159071 100644
--- a/pre_commit_hooks/trailing_whitespace_fixer.py
+++ b/pre_commit_hooks/trailing_whitespace_fixer.py
@@ -2,18 +2,44 @@
 
 import argparse
 import fileinput
+import os
 import sys
 
 from pre_commit_hooks.util import cmd_output
 
 
-def _fix_file(filename):
+def _fix_file(filename, markdown=False):
     for line in fileinput.input([filename], inplace=True):
+        # preserve trailing two-space for non-blank lines in markdown files
+        if markdown and (not line.isspace()) and (line.endswith("  \n")):
+            line = line.rstrip(' \n')
+            # only preserve if there are no trailing tabs or unusual whitespace
+            if not line[-1].isspace():
+                print(line + "  ")
+                continue
+
         print(line.rstrip())
 
 
 def fix_trailing_whitespace(argv=None):
     parser = argparse.ArgumentParser()
+    parser.add_argument(
+        '--no-markdown-linebreak-ext',
+        action='store_const',
+        const=[],
+        default=argparse.SUPPRESS,
+        dest='markdown_linebreak_ext',
+        help='Do not preserve linebreak spaces in Markdown'
+    )
+    parser.add_argument(
+        '--markdown-linebreak-ext',
+        action='append',
+        const='',
+        default=['md,markdown'],
+        metavar='*|EXT[,EXT,...]',
+        nargs='?',
+        help='Markdown extensions (or *) for linebreak spaces'
+    )
     parser.add_argument('filenames', nargs='*', help='Filenames to fix')
     args = parser.parse_args(argv)
 
@@ -21,10 +47,28 @@
         'grep', '-l', '[[:space:]]$', *args.filenames, retcode=None
     ).strip().splitlines()
 
+    md_args = args.markdown_linebreak_ext
+    if '' in md_args:
+        parser.error('--markdown-linebreak-ext requires a non-empty argument')
+    all_markdown = '*' in md_args
+    # normalize all extensions; split at ',', lowercase, and force 1 leading '.'
+    md_exts = ['.' + x.lower().lstrip('.')
+               for x in ','.join(md_args).split(',')]
+
+    # reject probable "eaten" filename as extension (skip leading '.' with [1:])
+    for ext in md_exts:
+        if any(c in ext[1:] for c in r'./\:'):
+            parser.error(
+                "bad --markdown-linebreak-ext extension '{0}' (has . / \\ :)\n"
+                "  (probably filename; use '--markdown-linebreak-ext=EXT')"
+                .format(ext)
+            )
+
     if bad_whitespace_files:
         for bad_whitespace_file in bad_whitespace_files:
             print('Fixing {0}'.format(bad_whitespace_file))
-            _fix_file(bad_whitespace_file)
+            _, extension = os.path.splitext(bad_whitespace_file.lower())
+            _fix_file(bad_whitespace_file, all_markdown or extension in md_exts)
         return 1
     else:
         return 0