diff --git a/Modules/_csv.c b/Modules/_csv.c
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -1658,30 +1658,34 @@ PyInit__csv(void)
     _csvstate(module)->field_limit = 128 * 1024;
     /* Do I still need to add this var to the Module Dict? */
 
     /* Add _dialects dictionary */
     _csvstate(module)->dialects = PyDict_New();
     if (_csvstate(module)->dialects == NULL)
         return NULL;
     Py_INCREF(_csvstate(module)->dialects);
-    if (PyModule_AddObject(module, "_dialects", _csvstate(module)->dialects))
+    if (PyModule_AddObject(module, "_dialects", _csvstate(module)->dialects) == -1) {
+        Py_DECREF(_csvstate(module)->dialects);
         return NULL;
+    }
 
     /* Add quote styles into dictionary */
     for (style = quote_styles; style->name; style++) {
         if (PyModule_AddIntConstant(module, style->name,
                                     style->style) == -1)
             return NULL;
     }
 
     /* Add the Dialect type */
     Py_INCREF(&Dialect_Type);
-    if (PyModule_AddObject(module, "Dialect", (PyObject *)&Dialect_Type))
+    if (PyModule_AddObject(module, "Dialect", (PyObject *)&Dialect_Type) == -1) {
+        Py_DECREF(&Dialect_Type);
         return NULL;
+    }
 
     /* Add the CSV exception object to the module. */
     _csvstate(module)->error_obj = PyErr_NewException("_csv.Error", NULL, NULL);
     if (_csvstate(module)->error_obj == NULL)
         return NULL;
     Py_INCREF(_csvstate(module)->error_obj);
     PyModule_AddObject(module, "Error", _csvstate(module)->error_obj);
     return module;