diff -r 9b053d3c74dc Lib/warnings.py
--- a/Lib/warnings.py	Wed Nov 16 15:56:50 2016 +0200
+++ b/Lib/warnings.py	Thu Nov 17 17:22:24 2016 +0100
@@ -148,18 +148,31 @@ def simplefilter(action, category=Warnin
            "lineno must be an int >= 0"
     _add_filter(action, None, category, None, lineno, append=append)

+def _pattern_key(pattern):
+    if pattern is not None:
+        return (pattern.pattern, pattern.flags)
+    else:
+        return ()
+
+def _cmp_key(item):
+    return (item[0], _pattern_key(item[1]), item[2], _pattern_key(item[3]))
+
 def _add_filter(*item, append):
     # Remove possible duplicate filters, so new one will be placed
     # in correct place. If append=True and duplicate exists, do nothing.
+    key = _cmp_key(item)
     if not append:
-        try:
-            filters.remove(item)
-        except ValueError:
-            pass
+        for index in range(len(filters)):
+            if _cmp_key(filters[index]) == key:
+                del filters[index]
+                break
+            print(_cmp_key(filters[index]), "!=", key)
+
         filters.insert(0, item)
     else:
-        if item not in filters:
-            filters.append(item)
+        if any(_cmp_key(filter) == key for filter in filters):
+            return
+        filters.append(item)
     _filters_mutated()

 def resetwarnings():