diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py
index ce2c22d..1877192 100644
--- a/Lib/test/test_struct.py
+++ b/Lib/test/test_struct.py
@@ -491,6 +491,9 @@
             self.test_unpack_from(cls=buffer)
 
     def test_bool(self):
+        class ExplodingBool(object):
+            def __nonzero__(self):
+                raise IOError
         for prefix in tuple("<>!=")+('',):
             false = (), [], [], '', 0
             true = [1], 'test', 5, -1, 0xffffffffL+1, 0xffffffff//2
@@ -519,8 +522,11 @@
                 self.assertFalse(prefix, msg='encoded bool is not one byte: %r'
                                              %packed)
 
-            for c in '\x01\x7f\xff\x0f\xf0':
-                self.assertTrue(struct.unpack('>?', c)[0])
+            self.assertRaises(IOError, struct.pack, prefix + '?',
+                              ExplodingBool())
+
+        for c in [b'\x01', b'\x7f', b'\xff', b'\x0f', b'\xf0']:
+            self.assertTrue(struct.unpack('>?', c)[0])
 
     @unittest.skipUnless(IS32BIT, "Specific to 32bit machines")
     def test_crasher(self):
diff --git a/Modules/_struct.c b/Modules/_struct.c
index 2eb461f..52c5eeb 100644
--- a/Modules/_struct.c
+++ b/Modules/_struct.c
@@ -636,9 +636,13 @@
 static int
 np_bool(char *p, PyObject *v, const formatdef *f)
 {
-    BOOL_TYPE y;
+    int y;
+    BOOL_TYPE x;
     y = PyObject_IsTrue(v);
-    memcpy(p, (char *)&y, sizeof y);
+    if (y < 0)
+        return -1;
+    x = y;
+    memcpy(p, (char *)&x, sizeof x);
     return 0;
 }
 
@@ -910,6 +914,8 @@
 {
     char y;
     y = PyObject_IsTrue(v);
+    if (y < 0)
+        return -1;
     memcpy(p, (char *)&y, sizeof y);
     return 0;
 }