diff -r b61690ba9432 Lib/test/test_xml_etree.py
--- a/Lib/test/test_xml_etree.py	Sat May 02 10:07:08 2015 -0700
+++ b/Lib/test/test_xml_etree.py	Sat May 02 23:33:12 2015 +0300
@@ -1708,6 +1708,123 @@ class BasicElementTest(ElementTestCase, 
                 self.assertEqual(e2.tag, 'group')
                 self.assertEqual(e2[0].tag, 'dogs')
 
+    def test_extend_mutable_list(self):
+        class X:
+            @property
+            def __class__(self):
+                L[:] = [ET.Element('baz')]
+                return ET.Element
+        L = [X()]
+        e = ET.Element('foo')
+        try:
+            e.extend(L)
+        except TypeError:
+            pass
+
+        class Y(X, ET.Element):
+            pass
+        L = [Y('x')]
+        e = ET.Element('foo')
+        e.extend(L)
+
+    def test_extend_mutable_list2(self):
+        class X:
+            @property
+            def __class__(self):
+                del L[:]
+                return ET.Element
+        L = [X(), ET.Element('baz')]
+        e = ET.Element('foo')
+        try:
+            e.extend(L)
+        except TypeError:
+            pass
+
+        class Y(X, ET.Element):
+            pass
+        L = [Y('bar'), ET.Element('baz')]
+        e = ET.Element('foo')
+        e.extend(L)
+
+    def test_remove_with_mutating(self):
+        class X(ET.Element):
+            def __eq__(self, o):
+                del e[:]
+                return False
+        e = ET.Element('foo')
+        e.extend([X('bar')])
+        self.assertRaises(ValueError, e.remove, ET.Element('baz'))
+
+        e = ET.Element('foo')
+        e.extend([ET.Element('bar')])
+        self.assertRaises(ValueError, e.remove, X('baz'))
+
+    def test_find_with_mutating(self):
+        class X(str):
+            def __eq__(self, o):
+                del e[:]
+                return True
+        X.__hash__ = str.__hash__
+        e = ET.Element('foo')
+        e.extend([ET.Element('bar')])
+        e.find(X('x'))
+
+    def test_find_with_error(self):
+        class X(str):
+            def __eq__(self, o):
+                1/0
+        X.__hash__ = str.__hash__
+        e = ET.Element('foo')
+        e.extend([ET.Element('bar')])
+        try:
+            e.find(X('x'))
+        except ZeroDivisionError:
+            pass
+
+    def test_findtext_with_mutating(self):
+        class X(str):
+            def __eq__(self, o):
+                del e[:]
+                return True
+        X.__hash__ = str.__hash__
+        e = ET.Element('foo')
+        e.extend([ET.Element('bar')])
+        e.findtext(X('x'))
+
+    def test_findtext_with_error(self):
+        class X(str):
+            def __eq__(self, o):
+                1/0
+        X.__hash__ = str.__hash__
+        e = ET.Element('foo')
+        e.extend([ET.Element('bar')])
+        try:
+            e.findtext(X('x'))
+        except ZeroDivisionError:
+            pass
+
+    def test_findall_with_mutating(self):
+        class X(str):
+            def __eq__(self, o):
+                del e[:]
+                return True
+        X.__hash__ = str.__hash__
+        e = ET.Element('foo')
+        e.extend([ET.Element('bar')])
+        e.findall(X('x'))
+
+    def test_findall_with_error(self):
+        class X(str):
+            def __eq__(self, o):
+                1/0
+        X.__hash__ = str.__hash__
+        e = ET.Element('foo')
+        e.extend([ET.Element('bar')])
+        try:
+            e.findall(X('x'))
+        except ZeroDivisionError:
+            pass
+
 
 class ElementTreeTypeTest(unittest.TestCase):
     def test_istype(self):
diff -r b61690ba9432 Modules/_elementtree.c
--- a/Modules/_elementtree.c	Sat May 02 10:07:08 2015 -0700
+++ b/Modules/_elementtree.c	Sat May 02 23:33:12 2015 +0300
@@ -1040,7 +1040,7 @@ static PyObject*
 element_extend(ElementObject* self, PyObject* args)
 {
     PyObject* seq;
-    Py_ssize_t i, seqlen = 0;
+    Py_ssize_t i;
 
     PyObject* seq_in;
     if (!PyArg_ParseTuple(args, "O:extend", &seq_in))
@@ -1055,22 +1055,29 @@ element_extend(ElementObject* self, PyOb
         return NULL;
     }
 
-    seqlen = PySequence_Size(seq);
-    for (i = 0; i < seqlen; i++) {
+    for (i = 0; i < PySequence_Fast_GET_SIZE(seq); i++) {
         PyObject* element = PySequence_Fast_GET_ITEM(seq, i);
-        if (!PyObject_IsInstance(element, (PyObject *)&Element_Type)) {
+        int rc;
+        Py_INCREF(element);
+        rc = PyObject_IsSubclass((PyObject *)Py_TYPE(element),
+                                 (PyObject *)&Element_Type);
+        if (rc <= 0) {
+            if (rc == 0)
+                PyErr_Format(
+                    PyExc_TypeError,
+                    "expected an Element, not \"%.200s\"",
+                    Py_TYPE(element)->tp_name);
             Py_DECREF(seq);
-            PyErr_Format(
-                PyExc_TypeError,
-                "expected an Element, not \"%.200s\"",
-                Py_TYPE(element)->tp_name);
+            Py_DECREF(element);
             return NULL;
         }
 
         if (element_add_subelement(self, element) < 0) {
             Py_DECREF(seq);
+            Py_DECREF(element);
             return NULL;
         }
+        Py_DECREF(element);
     }
 
     Py_DECREF(seq);
@@ -1103,11 +1110,16 @@ element_find(ElementObject *self, PyObje
 
     for (i = 0; i < self->extra->length; i++) {
         PyObject* item = self->extra->children[i];
-        if (Element_CheckExact(item) &&
-            PyObject_RichCompareBool(((ElementObject*)item)->tag, tag, Py_EQ) == 1) {
-            Py_INCREF(item);
+        int rc;
+        if (!Element_CheckExact(item))
+            continue;
+        Py_INCREF(item);
+        rc = PyObject_RichCompareBool(((ElementObject*)item)->tag, tag, Py_EQ);
+        if (rc > 0)
             return item;
-        }
+        Py_DECREF(item);
+        if (rc < 0)
+            return NULL;
     }
 
     Py_RETURN_NONE;
@@ -1140,14 +1152,24 @@ element_findtext(ElementObject *self, Py
 
     for (i = 0; i < self->extra->length; i++) {
         ElementObject* item = (ElementObject*) self->extra->children[i];
-        if (Element_CheckExact(item) &&
-            (PyObject_RichCompareBool(item->tag, tag, Py_EQ) == 1)) {
+        int rc;
+        if (!Element_CheckExact(item))
+            continue;
+        Py_INCREF(item);
+        rc = PyObject_RichCompareBool(item->tag, tag, Py_EQ);
+        if (rc > 0) {
             PyObject* text = element_get_text(item);
-            if (text == Py_None)
+            if (text == Py_None) {
+                Py_DECREF(item);
                 return PyUnicode_New(0, 0);
+            }
             Py_XINCREF(text);
+            Py_DECREF(item);
             return text;
         }
+        Py_DECREF(item);
+        if (rc < 0)
+            return NULL;
     }
 
     Py_INCREF(default_value);
@@ -1184,13 +1206,17 @@ element_findall(ElementObject *self, PyO
 
     for (i = 0; i < self->extra->length; i++) {
         PyObject* item = self->extra->children[i];
-        if (Element_CheckExact(item) &&
-            PyObject_RichCompareBool(((ElementObject*)item)->tag, tag, Py_EQ) == 1) {
-            if (PyList_Append(out, item) < 0) {
-                Py_DECREF(out);
-                return NULL;
-            }
+        int rc;
+        if (!Element_CheckExact(item))
+            continue;
+        Py_INCREF(item);
+        rc = PyObject_RichCompareBool(((ElementObject*)item)->tag, tag, Py_EQ);
+        if (rc != 0 && (rc < 0 || PyList_Append(out, item) < 0)) {
+            Py_DECREF(item);
+            Py_DECREF(out);
+            return NULL;
         }
+        Py_DECREF(item);
     }
 
     return out;
@@ -1405,8 +1431,10 @@ static PyObject*
 element_remove(ElementObject* self, PyObject* args)
 {
     Py_ssize_t i;
-
+    int rc;
     PyObject* element;
+    PyObject* found;
+
     if (!PyArg_ParseTuple(args, "O!:remove", &Element_Type, &element))
         return NULL;
 
@@ -1422,11 +1450,14 @@ element_remove(ElementObject* self, PyOb
     for (i = 0; i < self->extra->length; i++) {
         if (self->extra->children[i] == element)
             break;
-        if (PyObject_RichCompareBool(self->extra->children[i], element, Py_EQ) == 1)
+        rc = PyObject_RichCompareBool(self->extra->children[i], element, Py_EQ);
+        if (rc > 0)
             break;
+        if (rc < 0)
+            return NULL;
     }
 
-    if (i == self->extra->length) {
+    if (i >= self->extra->length) {
         /* element is not in children, so raise exception */
         PyErr_SetString(
             PyExc_ValueError,
@@ -1435,13 +1466,13 @@ element_remove(ElementObject* self, PyOb
         return NULL;
     }
 
-    Py_DECREF(self->extra->children[i]);
+    found = self->extra->children[i];
 
     self->extra->length--;
-
     for (; i < self->extra->length; i++)
         self->extra->children[i] = self->extra->children[i+1];
 
+    Py_DECREF(found);
     Py_RETURN_NONE;
 }
 
@@ -2014,6 +2045,7 @@ elementiter_next(ElementIterObject *it)
      */
     ElementObject *cur_parent;
     Py_ssize_t child_index;
+    int rc;
 
     while (1) {
         /* Handle the case reached in the beginning and end of iteration, where
@@ -2035,14 +2067,22 @@ elementiter_next(ElementIterObject *it)
                 }
 
                 it->root_done = 1;
-                if (it->sought_tag == Py_None ||
-                    PyObject_RichCompareBool(it->root_element->tag,
-                                             it->sought_tag, Py_EQ) == 1) {
+                rc = (it->sought_tag == Py_None);
+                if (!rc) {
+                    rc = PyObject_RichCompareBool(it->root_element->tag,
+                                                  it->sought_tag, Py_EQ);
+                    if (rc < 0)
+                        return NULL;
+                }
+                if (rc) {
                     if (it->gettext) {
                         PyObject *text = element_get_text(it->root_element);
                         if (!text)
                             return NULL;
-                        if (PyObject_IsTrue(text)) {
+                        rc = PyObject_IsTrue(text);
+                        if (rc < 0)
+                            return NULL;
+                        if (rc) {
                             Py_INCREF(text);
                             return text;
                         }
@@ -2074,18 +2114,26 @@ elementiter_next(ElementIterObject *it)
                 PyObject *text = element_get_text(child);
                 if (!text)
                     return NULL;
-                if (PyObject_IsTrue(text)) {
+                rc = PyObject_IsTrue(text);
+                if (rc < 0)
+                    return NULL;
+                if (rc) {
                     Py_INCREF(text);
                     return text;
                 }
-            } else if (it->sought_tag == Py_None ||
-                PyObject_RichCompareBool(child->tag,
-                                         it->sought_tag, Py_EQ) == 1) {
-                Py_INCREF(child);
-                return (PyObject *)child;
+            } else {
+                rc = (it->sought_tag == Py_None);
+                if (!rc) {
+                    rc = PyObject_RichCompareBool(child->tag,
+                                                  it->sought_tag, Py_EQ);
+                    if (rc < 0)
+                        return NULL;
+                }
+                if (rc) {
+                    Py_INCREF(child);
+                    return (PyObject *)child;
+                }
             }
-            else
-                continue;
         }
         else {
             PyObject *tail;
@@ -2105,9 +2153,14 @@ elementiter_next(ElementIterObject *it)
              * this is because itertext() is supposed to only return *inner*
              * text, not text following the element it began iteration with.
              */
-            if (it->parent_stack->parent && PyObject_IsTrue(tail)) {
-                Py_INCREF(tail);
-                return tail;
+            if (it->parent_stack->parent) {
+                rc = PyObject_IsTrue(tail);
+                if (rc < 0)
+                    return NULL;
+                if (rc) {
+                    Py_INCREF(tail);
+                    return tail;
+                }
             }
         }
     }
@@ -2165,20 +2218,21 @@ static PyObject *
 create_elementiter(ElementObject *self, PyObject *tag, int gettext)
 {
     ElementIterObject *it;
-    PyObject *star = NULL;
 
     it = PyObject_GC_New(ElementIterObject, &ElementIter_Type);
     if (!it)
         return NULL;
 
-    if (PyUnicode_Check(tag))
-        star = PyUnicode_FromString("*");
-    else if (PyBytes_Check(tag))
-        star = PyBytes_FromString("*");
-
-    if (star && PyObject_RichCompareBool(tag, star, Py_EQ) == 1)
-        tag = Py_None;
-    Py_XDECREF(star);
+    if (PyUnicode_Check(tag)) {
+        if (PyUnicode_READY(tag) == -1)
+            return NULL;
+        if (PyUnicode_GET_LENGTH(tag) == 1 && PyUnicode_READ_CHAR(tag, 0) == '*')
+            tag = Py_None;
+    }
+    else if (PyBytes_Check(tag)) {
+        if (PyBytes_GET_SIZE(tag) == 1 && *PyBytes_AS_STRING(tag) == '*')
+            tag = Py_None;
+    }
 
     Py_INCREF(tag);
     it->sought_tag = tag;