diff --git a/Lib/cgi.py b/Lib/cgi.py
index b4c620a..e7cd778 100755
--- a/Lib/cgi.py
+++ b/Lib/cgi.py
@@ -293,7 +293,7 @@ def _parseparam(s):
     while s[:1] == ';':
         s = s[1:]
         end = s.find(';')
-        while end > 0 and s.count('"', 0, end) % 2:
+        while end > 0 and (s.count('"', 0, end) - s.count('\\"', 0, end)) % 2:
             end = s.find(';', end + 1)
         if end < 0:
             end = len(s)
diff --git a/Lib/test/test_cgi.py b/Lib/test/test_cgi.py
index e282a51..63547b2 100644
--- a/Lib/test/test_cgi.py
+++ b/Lib/test/test_cgi.py
@@ -377,6 +377,9 @@ this is the content of the fake file
         self.assertEqual(
             cgi.parse_header('attachment; filename="strange;name";size=123;'),
             ("attachment", {"filename": "strange;name", "size": "123"}))
+        self.assertEqual(
+            cgi.parse_header('form-data; name="files"; filename="fo\\"o;bar"'),
+            ("form-data", {"name": "files", "filename": 'fo"o;bar'}))
 
 
 def test_main():