diff --git a/Modules/_csv.c b/Modules/_csv.c
index ea3add2..ab2a5ed 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -208,8 +208,12 @@
 {
     if (src == NULL)
         *target = dflt;
-    else
-        *target = PyObject_IsTrue(src);
+    else {
+        int b = PyObject_IsTrue(src);
+        if (b < 0)
+            return -1;
+        *target = b;
+    }
     return 0;
 }
 
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index 2662e4b..1746604 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -1013,8 +1013,11 @@
     res = PyObject_CallMethod(buffer, "seekable", NULL);
     if (res == NULL)
         goto error;
-    self->seekable = self->telling = PyObject_IsTrue(res);
+    r = PyObject_IsTrue(res);
     Py_DECREF(res);
+    if (r < 0)
+        goto error;
+    self->seekable = self->telling = r;
 
     self->encoding_start_of_stream = 0;
     if (self->seekable && self->encoder) {
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index e692b5d..195e5b6 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -1005,6 +1005,7 @@
     int len;
     int verification;
     PyObject *binary_mode = Py_None;
+    int b;
 
     if (!PyArg_ParseTuple(args, "|O:peer_certificate", &binary_mode))
         return NULL;
@@ -1012,7 +1013,10 @@
     if (!self->peer_cert)
         Py_RETURN_NONE;
 
-    if (PyObject_IsTrue(binary_mode)) {
+    b = PyObject_IsTrue(binary_mode);
+    if (b < 0)
+        return NULL;
+    if (b) {
         /* return cert in DER-encoded format */
 
         unsigned char *bytes_buf = NULL;
diff --git a/Modules/cStringIO.c b/Modules/cStringIO.c
index 89f1dd6..a19a31e 100644
--- a/Modules/cStringIO.c
+++ b/Modules/cStringIO.c
@@ -127,12 +127,16 @@
 static PyObject *
 IO_getval(IOobject *self, PyObject *args) {
     PyObject *use_pos=Py_None;
+    int b;
     Py_ssize_t s;
 
     if (!IO__opencheck(self)) return NULL;
     if (!PyArg_UnpackTuple(args,"getval", 0, 1,&use_pos)) return NULL;
 
-    if (PyObject_IsTrue(use_pos)) {
+    b = PyObject_IsTrue(use_pos);
+    if (b < 0)
+        return NULL;
+    if (b) {
               s=self->pos;
               if (s > self->string_size) s=self->string_size;
     }
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index b51ccf9..f6d0e23 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -903,11 +903,13 @@
         }
         ok = PyObject_IsTrue(good);
         Py_DECREF(good);
-        if (!ok) {
+        if (ok == 0) {
             lz->start = 1;
             return item;
         }
         Py_DECREF(item);
+        if (ok < 0)
+            return NULL;
     }
 }
 
@@ -1043,10 +1045,11 @@
     }
     ok = PyObject_IsTrue(good);
     Py_DECREF(good);
-    if (ok)
+    if (ok > 0)
         return item;
     Py_DECREF(item);
-    lz->stop = 1;
+    if (ok == 0)
+        lz->stop = 1;
     return NULL;
 }
 
@@ -3001,9 +3004,11 @@
             ok = PyObject_IsTrue(good);
             Py_DECREF(good);
         }
-        if (ok)
+        if (ok > 0)
             return item;
         Py_DECREF(item);
+        if (ok < 0)
+            return NULL;
     }
 }
 
@@ -3144,9 +3149,11 @@
             ok = PyObject_IsTrue(good);
             Py_DECREF(good);
         }
-        if (!ok)
+        if (ok == 0)
             return item;
         Py_DECREF(item);
+        if (ok < 0)
+            return NULL;
     }
 }
 
diff --git a/Modules/parsermodule.c b/Modules/parsermodule.c
index 462cb74..8e581c2 100644
--- a/Modules/parsermodule.c
+++ b/Modules/parsermodule.c
@@ -350,10 +350,14 @@
         int lineno = 0;
         int col_offset = 0;
         if (line_option != NULL) {
-            lineno = (PyObject_IsTrue(line_option) != 0) ? 1 : 0;
+            lineno = PyObject_IsTrue(line_option);
+            if (lineno < 0)
+                return NULL;
         }
         if (col_option != NULL) {
-            col_offset = (PyObject_IsTrue(col_option) != 0) ? 1 : 0;
+            col_offset = PyObject_IsTrue(col_option);
+            if (col_offset < 0)
+                return NULL;
         }
         /*
          *  Convert ST into a tuple representation.  Use Guido's function,
@@ -401,10 +405,14 @@
         int lineno = 0;
         int col_offset = 0;
         if (line_option != 0) {
-            lineno = PyObject_IsTrue(line_option) ? 1 : 0;
+            lineno = PyObject_IsTrue(line_option);
+            if (lineno < 0)
+                return NULL;
         }
-        if (col_option != NULL) {
-            col_offset = (PyObject_IsTrue(col_option) != 0) ? 1 : 0;
+        if (col_option != 0) {
+            col_offset = PyObject_IsTrue(col_option);
+            if (col_offset < 0)
+                return NULL;
         }
         /*
          *  Convert ST into a tuple representation.  Use Guido's function,
diff --git a/Modules/pyexpat.c b/Modules/pyexpat.c
index 976908c..4d9a1e5 100644
--- a/Modules/pyexpat.c
+++ b/Modules/pyexpat.c
@@ -1174,13 +1174,16 @@
 xmlparse_UseForeignDTD(xmlparseobject *self, PyObject *args)
 {
     PyObject *flagobj = NULL;
-    XML_Bool flag = XML_TRUE;
+    int flag = 1;
     enum XML_Error rc;
-    if (!PyArg_UnpackTuple(args, "UseForeignDTD", 0, 1, &flagobj))
+    if (!PyArg_ParseTuple(args, "O:UseForeignDTD", &flagobj))
         return NULL;
-    if (flagobj != NULL)
-        flag = PyObject_IsTrue(flagobj) ? XML_TRUE : XML_FALSE;
-    rc = XML_UseForeignDTD(self->itself, flag);
+    if (flagobj != NULL) {
+        flag = PyObject_IsTrue(flagobj);
+        if (flag < 0)
+            return NULL;
+    }
+    rc = XML_UseForeignDTD(self->itself, flag ? XML_TRUE : XML_FALSE);
     if (rc != XML_ERROR_NONE) {
         return set_error(self, rc);
     }
@@ -1549,7 +1552,10 @@
         return -1;
     }
     if (strcmp(name, "buffer_text") == 0) {
-        if (PyObject_IsTrue(v)) {
+        int b = PyObject_IsTrue(v);
+        if (b < 0)
+            return -1;
+        if (b) {
             if (self->buffer == NULL) {
                 self->buffer = malloc(self->buffer_size);
                 if (self->buffer == NULL) {
@@ -1568,39 +1574,39 @@
         return 0;
     }
     if (strcmp(name, "namespace_prefixes") == 0) {
-        if (PyObject_IsTrue(v))
-            self->ns_prefixes = 1;
-        else
-            self->ns_prefixes = 0;
+        int b = PyObject_IsTrue(v);
+        if (b < 0)
+            return -1;
+        self->ns_prefixes = b;
         XML_SetReturnNSTriplet(self->itself, self->ns_prefixes);
         return 0;
     }
     if (strcmp(name, "ordered_attributes") == 0) {
-        if (PyObject_IsTrue(v))
-            self->ordered_attributes = 1;
-        else
-            self->ordered_attributes = 0;
+        int b = PyObject_IsTrue(v);
+        if (b < 0)
+            return -1;
+        self->ordered_attributes = b;
         return 0;
     }
     if (strcmp(name, "returns_unicode") == 0) {
-        if (PyObject_IsTrue(v)) {
+        int b = PyObject_IsTrue(v);
+        if (b < 0)
+            return -1;
 #ifndef Py_USING_UNICODE
+        if (b) {
             PyErr_SetString(PyExc_ValueError,
                             "Unicode support not available");
             return -1;
-#else
-            self->returns_unicode = 1;
-#endif
         }
-        else
-            self->returns_unicode = 0;
+#endif
+        self->returns_unicode = b;
         return 0;
     }
     if (strcmp(name, "specified_attributes") == 0) {
-        if (PyObject_IsTrue(v))
-            self->specified_attributes = 1;
-        else
-            self->specified_attributes = 0;
+        int b = PyObject_IsTrue(v);
+        if (b < 0)
+            return -1;
+        self->specified_attributes = b;
         return 0;
     }