diff --git a/Objects/setobject.c b/Objects/setobject.c
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -25,17 +25,17 @@
 
    Unlike the dictionary implementation, the lookkey functions can return
    NULL if the rich comparison returns an error.
+
+   Another difference from the dictionary implementation is that the lookkey
+   functions can never return a dummy entry.  The means that dummy entries do
+   not get reused.  The benefit is that the code for lookkey, insert, discard,
+   and contains is simplified.
 */
 
 #include "Python.h"
 #include "structmember.h"
 #include "stringlib/eq.h"
 
-/* Object used as dummy key to fill deleted entries */
-static PyObject _dummy_struct;
-
-#define dummy (&_dummy_struct)
-
 
 /* ======================================================================== */
 /* ======= Begin logic for probing the hash table ========================= */
@@ -48,11 +48,14 @@
 /* This must be >= 1 */
 #define PERTURB_SHIFT 5
 
+/* Object used as dummy key to fill deleted entries */
+static PyObject _dummy_struct;
+#define dummy (&_dummy_struct)
+
 static setentry *
 set_lookkey(PySetObject *so, PyObject *key, Py_hash_t hash)
 {
     setentry *table = so->table;
-    setentry *freeslot = NULL;
     setentry *entry;
     size_t perturb = hash;
     size_t mask = so->mask;
@@ -79,13 +82,11 @@
             if (cmp > 0)                                          /* likely */
                 return entry;
         }
-        if (entry->key == dummy && freeslot == NULL)
-            freeslot = entry;
 
         for (j = 1 ; j <= LINEAR_PROBES ; j++) {
             entry = &table[(i + j) & mask];
             if (entry->key == NULL)
-                goto found_null;
+                return entry;
             if (entry->hash == hash && entry->key != dummy) {
                 PyObject *startkey = entry->key;
                 if (startkey == key)
@@ -100,8 +101,6 @@
                 if (cmp > 0)
                     return entry;
             }
-            if (entry->key == dummy && freeslot == NULL)
-                freeslot = entry;
         }
 
         perturb >>= PERTURB_SHIFT;
@@ -109,10 +108,9 @@
 
         entry = &table[i & mask];
         if (entry->key == NULL)
-            goto found_null;
+            return entry;
     }
-  found_null:
-    return freeslot == NULL ? entry : freeslot;
+    assert(0);
 }
 
 /*
@@ -124,7 +122,6 @@
 set_lookkey_unicode(PySetObject *so, PyObject *key, Py_hash_t hash)
 {
     setentry *table = so->table;
-    setentry *freeslot = NULL;
     setentry *entry;
     size_t perturb = hash;
     size_t mask = so->mask;
@@ -150,20 +147,16 @@
                 || (entry->key != dummy                           /* unlikely */
                     && unicode_eq(entry->key, key))))             /* likely */
             return entry;
-        if (entry->key == dummy && freeslot == NULL)
-            freeslot = entry;
 
         for (j = 1 ; j <= LINEAR_PROBES ; j++) {
             entry = &table[(i + j) & mask];
             if (entry->key == NULL)
-                goto found_null;
+                return entry;
             if (entry->hash == hash
                 && (entry->key == key
                     || (entry->key != dummy                       /* unlikely */
                         && unicode_eq(entry->key, key))))         /* likely */
                 return entry;
-            if (entry->key == dummy && freeslot == NULL)
-                freeslot = entry;
         }
 
         perturb >>= PERTURB_SHIFT;
@@ -171,10 +164,9 @@
 
         entry = &table[i & mask];
         if (entry->key == NULL)
-            goto found_null;
+            return entry;
     }
-  found_null:
-    return freeslot == NULL ? entry : freeslot;
+    assert(0);
 }
 
 /*
@@ -229,17 +221,13 @@
     entry = so->lookup(so, key, hash);
     if (entry == NULL)
         return -1;
+    assert(entry->key != dummy);
     if (entry->key == NULL) {
         /* UNUSED */
         entry->key = key;
         entry->hash = hash;
         so->fill++;
         so->used++;
-    } else if (entry->key == dummy) {
-        /* DUMMY */
-        entry->key = key;
-        entry->hash = hash;
-        so->used++;
     } else {
         /* ACTIVE */
         Py_DECREF(key);
@@ -388,7 +376,8 @@
     entry = (so->lookup)(so, oldentry->key, oldentry->hash);
     if (entry == NULL)
         return -1;
-    if (entry->key == NULL  ||  entry->key == dummy)
+    assert(entry->key != dummy);
+    if (entry->key == NULL)
         return DISCARD_NOTFOUND;
     old_key = entry->key;
     entry->key = dummy;
@@ -635,7 +624,8 @@
     if (lu_entry == NULL)
         return -1;
     key = lu_entry->key;
-    return key != NULL && key != dummy;
+    assert(key != dummy);
+    return key != NULL;
 }
 
 static int