diff --git a/Doc/includes/custom.c b/Doc/includes/custom.c
index 13d16f5..bda32e2 100644
--- a/Doc/includes/custom.c
+++ b/Doc/includes/custom.c
@@ -35,6 +35,11 @@
         return NULL;
 
     Py_INCREF(&CustomType);
-    PyModule_AddObject(m, "Custom", (PyObject *) &CustomType);
+    if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) {
+        Py_DECREF(&CustomType);
+        PY_DECREF(m);
+        return NULL;
+    }
+
     return m;
 }
diff --git a/Doc/includes/custom2.c b/Doc/includes/custom2.c
index 6477a19..5bacab7 100644
--- a/Doc/includes/custom2.c
+++ b/Doc/includes/custom2.c
@@ -128,6 +128,11 @@
         return NULL;
 
     Py_INCREF(&CustomType);
-    PyModule_AddObject(m, "Custom", (PyObject *) &CustomType);
+    if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) {
+        Py_DECREF(&CustomType);
+        Py_DECREF(m);
+        return NULL;
+    }
+
     return m;
 }
diff --git a/Doc/includes/custom3.c b/Doc/includes/custom3.c
index 213d086..2b7a99e 100644
--- a/Doc/includes/custom3.c
+++ b/Doc/includes/custom3.c
@@ -179,6 +179,11 @@
         return NULL;
 
     Py_INCREF(&CustomType);
-    PyModule_AddObject(m, "Custom", (PyObject *) &CustomType);
+    if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) {
+        Py_DECREF(&CustomType);
+        Py_DECREF(m);
+        return NULL;
+    }
+
     return m;
 }
diff --git a/Doc/includes/custom4.c b/Doc/includes/custom4.c
index b0b2906..584992f 100644
--- a/Doc/includes/custom4.c
+++ b/Doc/includes/custom4.c
@@ -193,6 +193,11 @@
         return NULL;
 
     Py_INCREF(&CustomType);
-    PyModule_AddObject(m, "Custom", (PyObject *) &CustomType);
+    if (PyModule_AddObject(m, "Custom", (PyObject *) &CustomType) < 0) {
+        Py_DECREF(&CustomType);
+        Py_DECREF(m);
+        return NULL;
+    }
+
     return m;
 }
diff --git a/Doc/includes/sublist.c b/Doc/includes/sublist.c
index 76ff939..b2c26e7 100644
--- a/Doc/includes/sublist.c
+++ b/Doc/includes/sublist.c
@@ -59,6 +59,11 @@
         return NULL;
 
     Py_INCREF(&SubListType);
-    PyModule_AddObject(m, "SubList", (PyObject *) &SubListType);
+    if (PyModule_AddObject(m, "SubList", (PyObject *) &SubListType) < 0) {
+        Py_DECREF(&SubListType);
+        Py_DECREF(m);
+        return NULL;
+    }
+
     return m;
 }