diff --git a/Objects/setobject.c b/Objects/setobject.c
index 9fe2813..c1bc1e1 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -1550,20 +1550,26 @@
     PyObject *key;
     Py_hash_t hash;
     setentry *entry;
-    Py_ssize_t pos = 0;
+    Py_ssize_t pos = 0, other_size;
     int rv;
 
     if (PySet_GET_SIZE(so) == 0) {
         return set_copy(so);
     }
 
-    if (!PyAnySet_Check(other)  && !PyDict_CheckExact(other)) {
+    if (PyAnySet_Check(other)) {
+        other_size = PySet_GET_SIZE(other);
+    }
+    else if (PyDict_CheckExact(other)) {
+        other_size = PyDict_Size(other);
+    }
+    else {
         return set_copy_and_difference(so, other);
     }
 
     /* If len(so) much more than len(other), it's more efficient to simply copy
      * so and then iterate other looking for common elements. */
-    if ((PySet_GET_SIZE(so) >> 2) > PyObject_Size(other)) {
+    if ((PySet_GET_SIZE(so) >> 2) > other_size) {
         return set_copy_and_difference(so, other);
     }