diff -r ac0d6c09457e Objects/setobject.c
--- a/Objects/setobject.c	Sun Jan 18 21:25:15 2015 -0800
+++ b/Objects/setobject.c	Tue Jan 20 12:30:18 2015 +0200
@@ -61,14 +61,15 @@ set_lookkey(PySetObject *so, PyObject *k
     int cmp;
 
     entry = &table[i & mask];
+    if (entry->key == key)
+        return entry;
     if (entry->key == NULL)
         return entry;
 
     while (1) {
-        if (entry->hash == hash && entry->key != dummy) {         /* dummy match unlikely */
+        if (entry->hash == hash) {
             PyObject *startkey = entry->key;
-            if (startkey == key)
-                return entry;
+            assert(startkey != dummy);
             Py_INCREF(startkey);
             cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
             Py_DECREF(startkey);
@@ -79,17 +80,18 @@ set_lookkey(PySetObject *so, PyObject *k
             if (cmp > 0)                                          /* likely */
                 return entry;
         }
-        if (entry->key == dummy && freeslot == NULL)
+        else if (entry->key == dummy && freeslot == NULL)
             freeslot = entry;
 
         for (j = 1 ; j <= LINEAR_PROBES ; j++) {
             entry = &table[(i + j) & mask];
+            if (entry->key == key)
+                return entry;
             if (entry->key == NULL)
                 goto found_null;
-            if (entry->hash == hash && entry->key != dummy) {
+            if (entry->hash == hash) {
                 PyObject *startkey = entry->key;
-                if (startkey == key)
-                    return entry;
+                assert(startkey != dummy);
                 Py_INCREF(startkey);
                 cmp = PyObject_RichCompareBool(startkey, key, Py_EQ);
                 Py_DECREF(startkey);
@@ -100,7 +102,7 @@ set_lookkey(PySetObject *so, PyObject *k
                 if (cmp > 0)
                     return entry;
             }
-            if (entry->key == dummy && freeslot == NULL)
+            else if (entry->key == dummy && freeslot == NULL)
                 freeslot = entry;
         }
 
@@ -108,6 +110,8 @@ set_lookkey(PySetObject *so, PyObject *k
         i = i * 5 + 1 + perturb;
 
         entry = &table[i & mask];
+        if (entry->key == key)
+            return entry;
         if (entry->key == NULL)
             goto found_null;
     }
@@ -131,6 +135,9 @@ set_lookkey_unicode(PySetObject *so, PyO
     size_t i = (size_t)hash;
     size_t j;
 
+    entry = &table[i & mask];
+    if (entry->key == key)
+        return entry;
     /* Make sure this function doesn't have to handle non-unicode keys,
        including subclasses of str; e.g., one reason to subclass
        strings is to override __eq__, and for speed we don't cater to
@@ -139,30 +146,28 @@ set_lookkey_unicode(PySetObject *so, PyO
         so->lookup = set_lookkey;
         return set_lookkey(so, key, hash);
     }
-
-    entry = &table[i & mask];
     if (entry->key == NULL)
         return entry;
 
     while (1) {
-        if (entry->hash == hash
-            && (entry->key == key
-                || (entry->key != dummy                           /* unlikely */
-                    && unicode_eq(entry->key, key))))             /* likely */
+        if (entry->hash == hash && unicode_eq(entry->key, key)) {
+            assert(entry->key != dummy);
             return entry;
-        if (entry->key == dummy && freeslot == NULL)
+        }
+        else if (entry->key == dummy && freeslot == NULL)
             freeslot = entry;
 
         for (j = 1 ; j <= LINEAR_PROBES ; j++) {
             entry = &table[(i + j) & mask];
+            if (entry->key == key)
+                return entry;
             if (entry->key == NULL)
                 goto found_null;
-            if (entry->hash == hash
-                && (entry->key == key
-                    || (entry->key != dummy                       /* unlikely */
-                        && unicode_eq(entry->key, key))))         /* likely */
+            if (entry->hash == hash && unicode_eq(entry->key, key)) {
+                assert(entry->key != dummy);
                 return entry;
-            if (entry->key == dummy && freeslot == NULL)
+            }
+            else if (entry->key == dummy && freeslot == NULL)
                 freeslot = entry;
         }
 
@@ -170,6 +175,8 @@ set_lookkey_unicode(PySetObject *so, PyO
         i = i * 5 + 1 + perturb;
 
         entry = &table[i & mask];
+        if (entry->key == key)
+            return entry;
         if (entry->key == NULL)
             goto found_null;
     }
@@ -392,6 +399,7 @@ set_discard_entry(PySetObject *so, seten
         return DISCARD_NOTFOUND;
     old_key = entry->key;
     entry->key = dummy;
+    entry->hash = -1;
     so->used--;
     Py_DECREF(old_key);
     return DISCARD_FOUND;
@@ -676,6 +684,7 @@ set_pop(PySetObject *so)
     }
     key = entry->key;
     entry->key = dummy;
+    entry->hash = -1;
     so->used--;
     so->finger = i + 1;         /* next place to start */
     return key;