diff --git a/src/if_py_both.h b/src/if_py_both.h
index 9e6c675..4905bed 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -700,7 +700,10 @@
 	}
 	else
 	{
-	    if (PyObject_IsTrue(val))
+	    int		istrue = PyObject_IsTrue(val);
+	    if (istrue == -1)
+		return -1;
+	    else if (istrue)
 		this->dict->dv_lock = VAR_LOCKED;
 	    else
 		this->dict->dv_lock = 0;
@@ -1201,7 +1204,10 @@
 	}
 	else
 	{
-	    if (PyObject_IsTrue(val))
+	    int		istrue = PyObject_IsTrue(val);
+	    if (istrue == -1)
+		return -1;
+	    else if (istrue)
 		this->list->lv_lock = VAR_LOCKED;
 	    else
 		this->list->lv_lock = 0;
@@ -1479,7 +1485,10 @@
 
     if (flags & SOPT_BOOL)
     {
-	r = set_option_value_for(key, PyObject_IsTrue(valObject), NULL,
+	int	istrue = PyObject_IsTrue(valObject);
+	if (istrue == -1)
+	    return -1;
+	r = set_option_value_for(key, istrue, NULL,
 				opt_flags, this->opt_type, this->from);
     }
     else if (flags & SOPT_NUM)