diff --git a/lib/py/src/ext/module.cpp b/lib/py/src/ext/module.cpp
index 7158b8f..f14ddae 100644
--- a/lib/py/src/ext/module.cpp
+++ b/lib/py/src/ext/module.cpp
@@ -48,20 +48,20 @@
 template <typename T>
 static PyObject* encode_impl(PyObject* args) {
   if (!args)
-    return NULL;
+    return nullptr;
 
-  PyObject* enc_obj = NULL;
-  PyObject* type_args = NULL;
+  PyObject* enc_obj = nullptr;
+  PyObject* type_args = nullptr;
   if (!PyArg_ParseTuple(args, "OO", &enc_obj, &type_args)) {
-    return NULL;
+    return nullptr;
   }
   if (!enc_obj || !type_args) {
-    return NULL;
+    return nullptr;
   }
 
   T protocol;
   if (!protocol.prepareEncodeBuffer() || !protocol.encodeValue(enc_obj, T_STRUCT, type_args)) {
-    return NULL;
+    return nullptr;
   }
 
   return protocol.getEncodedValue();
@@ -79,11 +79,11 @@
 
 template <typename T>
 static PyObject* decode_impl(PyObject* args) {
-  PyObject* output_obj = NULL;
-  PyObject* oprot = NULL;
-  PyObject* typeargs = NULL;
+  PyObject* output_obj = nullptr;
+  PyObject* oprot = nullptr;
+  PyObject* typeargs = nullptr;
   if (!PyArg_ParseTuple(args, "OOO", &output_obj, &oprot, &typeargs)) {
-    return NULL;
+    return nullptr;
   }
 
   T protocol;
@@ -96,16 +96,16 @@
                           default_limit));
   ScopedPyObject transport(PyObject_GetAttr(oprot, INTERN_STRING(trans)));
   if (!transport) {
-    return NULL;
+    return nullptr;
   }
 
   StructTypeArgs parsedargs;
   if (!parse_struct_args(&parsedargs, typeargs)) {
-    return NULL;
+    return nullptr;
   }
 
   if (!protocol.prepareDecodeBufferFromTransport(transport.get())) {
-    return NULL;
+    return nullptr;
   }
 
   return protocol.readStruct(output_obj, parsedargs.klass, parsedargs.spec);
@@ -141,22 +141,22 @@
     {"decode_binary", decode_binary, METH_VARARGS, ""},
     {"encode_compact", encode_compact, METH_VARARGS, ""},
     {"decode_compact", decode_compact, METH_VARARGS, ""},
-    {NULL, NULL, 0, NULL} /* Sentinel */
+    {nullptr, nullptr, 0, nullptr} /* Sentinel */
 };
 
 #if PY_MAJOR_VERSION >= 3
 
 static struct PyModuleDef ThriftFastBinaryDef = {PyModuleDef_HEAD_INIT,
                                                  "thrift.protocol.fastbinary",
-                                                 NULL,
+                                                 nullptr,
                                                  0,
                                                  ThriftFastBinaryMethods,
-                                                 NULL,
-                                                 NULL,
-                                                 NULL,
-                                                 NULL};
+                                                 nullptr,
+                                                 nullptr,
+                                                 nullptr,
+                                                 nullptr};
 
-#define INITERROR return NULL;
+#define INITERROR return nullptr;
 
 PyObject* PyInit_fastbinary() {
 
@@ -167,7 +167,7 @@
 void initfastbinary() {
 
   PycString_IMPORT;
-  if (PycStringIO == NULL)
+  if (PycStringIO == nullptr)
     INITERROR
 
 #endif
@@ -193,7 +193,7 @@
 #else
       Py_InitModule("thrift.protocol.fastbinary", ThriftFastBinaryMethods);
 #endif
-  if (module == NULL)
+  if (module == nullptr)
     INITERROR;
 
 #if PY_MAJOR_VERSION >= 3
diff --git a/lib/py/src/ext/protocol.h b/lib/py/src/ext/protocol.h
index 521b7ee..c0cd437 100644
--- a/lib/py/src/ext/protocol.h
+++ b/lib/py/src/ext/protocol.h
@@ -35,7 +35,7 @@
   ProtocolBase()
     : stringLimit_((std::numeric_limits<int32_t>::max)()),
       containerLimit_((std::numeric_limits<int32_t>::max)()),
-      output_(NULL) {}
+      output_(nullptr) {}
   inline virtual ~ProtocolBase();
 
   bool prepareDecodeBufferFromTransport(PyObject* trans);
diff --git a/lib/py/src/ext/protocol.tcc b/lib/py/src/ext/protocol.tcc
index ede2bb4..03cfc9b 100644
--- a/lib/py/src/ext/protocol.tcc
+++ b/lib/py/src/ext/protocol.tcc
@@ -48,7 +48,7 @@
     PycString_IMPORT;
   }
   if (!PycStringIO) {
-    return NULL;
+    return nullptr;
   }
   return PycStringIO->NewOutput(size);
 }
@@ -83,7 +83,7 @@
     PycString_IMPORT;
   }
   if (!PycStringIO) {
-    return NULL;
+    return nullptr;
   }
   return PycStringIO->cgetvalue(output_);
 }
@@ -277,7 +277,7 @@
   } else {
     // using building functions as this is a rare codepath
     ScopedPyObject newiobuf(PyObject_CallFunction(input_.refill_callable.get(), refill_signature,
-                                                  *output, rlen, len, NULL));
+                                                  *output, rlen, len, nullptr));
     if (!newiobuf) {
       return false;
     }
@@ -332,7 +332,7 @@
 template <typename Impl>
 bool ProtocolBase<Impl>::prepareEncodeBuffer() {
   output_ = detail::new_encode_buffer(INIT_OUTBUF_SIZE);
-  return output_ != NULL;
+  return output_ != nullptr;
 }
 
 template <typename Impl>
@@ -484,8 +484,8 @@
       return false;
     }
     Py_ssize_t pos = 0;
-    PyObject* k = NULL;
-    PyObject* v = NULL;
+    PyObject* k = nullptr;
+    PyObject* v = nullptr;
     // TODO(bmaurer): should support any mapping, not just dicts
     while (PyDict_Next(value, &pos, &k, &v)) {
       if (!encodeValue(k, parsedargs.ktag, parsedargs.ktypeargs)
@@ -647,7 +647,7 @@
   case T_BOOL: {
     bool v = 0;
     if (!impl()->readBool(v)) {
-      return NULL;
+      return nullptr;
     }
     if (v) {
       Py_RETURN_TRUE;
@@ -658,21 +658,21 @@
   case T_I08: {
     int8_t v = 0;
     if (!impl()->readI8(v)) {
-      return NULL;
+      return nullptr;
     }
     return PyInt_FromLong(v);
   }
   case T_I16: {
     int16_t v = 0;
     if (!impl()->readI16(v)) {
-      return NULL;
+      return nullptr;
     }
     return PyInt_FromLong(v);
   }
   case T_I32: {
     int32_t v = 0;
     if (!impl()->readI32(v)) {
-      return NULL;
+      return nullptr;
     }
     return PyInt_FromLong(v);
   }
@@ -680,7 +680,7 @@
   case T_I64: {
     int64_t v = 0;
     if (!impl()->readI64(v)) {
-      return NULL;
+      return nullptr;
     }
     // TODO(dreiss): Find out if we can take this fastpath always when
     //               sizeof(long) == sizeof(long long).
@@ -693,16 +693,16 @@
   case T_DOUBLE: {
     double v = 0.0;
     if (!impl()->readDouble(v)) {
-      return NULL;
+      return nullptr;
     }
     return PyFloat_FromDouble(v);
   }
 
   case T_STRING: {
-    char* buf = NULL;
+    char* buf = nullptr;
     int len = impl()->readString(&buf);
     if (len < 0) {
-      return NULL;
+      return nullptr;
     }
     if (isUtf8(typeargs)) {
       return PyUnicode_DecodeUTF8(buf, len, 0);
@@ -715,28 +715,28 @@
   case T_SET: {
     SetListTypeArgs parsedargs;
     if (!parse_set_list_args(&parsedargs, typeargs)) {
-      return NULL;
+      return nullptr;
     }
 
     TType etype = T_STOP;
     int32_t len = impl()->readListBegin(etype);
     if (len < 0) {
-      return NULL;
+      return nullptr;
     }
     if (len > 0 && !checkType(etype, parsedargs.element_type)) {
-      return NULL;
+      return nullptr;
     }
 
     bool use_tuple = type == T_LIST && parsedargs.immutable;
     ScopedPyObject ret(use_tuple ? PyTuple_New(len) : PyList_New(len));
     if (!ret) {
-      return NULL;
+      return nullptr;
     }
 
     for (int i = 0; i < len; i++) {
       PyObject* item = decodeValue(etype, parsedargs.typeargs);
       if (!item) {
-        return NULL;
+        return nullptr;
       }
       if (use_tuple) {
         PyTuple_SET_ITEM(ret.get(), i, item);
@@ -758,32 +758,32 @@
   case T_MAP: {
     MapTypeArgs parsedargs;
     if (!parse_map_args(&parsedargs, typeargs)) {
-      return NULL;
+      return nullptr;
     }
 
     TType ktype = T_STOP;
     TType vtype = T_STOP;
     uint32_t len = impl()->readMapBegin(ktype, vtype);
     if (len > 0 && (!checkType(ktype, parsedargs.ktag) || !checkType(vtype, parsedargs.vtag))) {
-      return NULL;
+      return nullptr;
     }
 
     ScopedPyObject ret(PyDict_New());
     if (!ret) {
-      return NULL;
+      return nullptr;
     }
 
     for (uint32_t i = 0; i < len; i++) {
       ScopedPyObject k(decodeValue(ktype, parsedargs.ktypeargs));
       if (!k) {
-        return NULL;
+        return nullptr;
       }
       ScopedPyObject v(decodeValue(vtype, parsedargs.vtypeargs));
       if (!v) {
-        return NULL;
+        return nullptr;
       }
       if (PyDict_SetItem(ret.get(), k.get(), v.get()) == -1) {
-        return NULL;
+        return nullptr;
       }
     }
 
@@ -792,12 +792,12 @@
         ThriftModule = PyImport_ImportModule("thrift.Thrift");
       }
       if (!ThriftModule) {
-        return NULL;
+        return nullptr;
       }
 
       ScopedPyObject cls(PyObject_GetAttr(ThriftModule, INTERN_STRING(TFrozenDict)));
       if (!cls) {
-        return NULL;
+        return nullptr;
       }
 
       ScopedPyObject arg(PyTuple_New(1));
@@ -811,7 +811,7 @@
   case T_STRUCT: {
     StructTypeArgs parsedargs;
     if (!parse_struct_args(&parsedargs, typeargs)) {
-      return NULL;
+      return nullptr;
     }
     return readStruct(Py_None, parsedargs.klass, parsedargs.spec);
   }
@@ -823,7 +823,7 @@
   case T_U64:
   default:
     PyErr_Format(PyExc_TypeError, "Unexpected TType for decodeValue: %d", type);
-    return NULL;
+    return nullptr;
   }
 }
 
@@ -833,26 +833,26 @@
   bool immutable = output == Py_None;
   ScopedPyObject kwargs;
   if (spec_seq_len == -1) {
-    return NULL;
+    return nullptr;
   }
 
   if (immutable) {
     kwargs.reset(PyDict_New());
     if (!kwargs) {
       PyErr_SetString(PyExc_TypeError, "failed to prepare kwargument storage");
-      return NULL;
+      return nullptr;
     }
   }
 
   detail::ReadStructScope<Impl> scope = detail::readStructScope(this);
   if (!scope) {
-    return NULL;
+    return nullptr;
   }
   while (true) {
     TType type = T_STOP;
     int16_t tag;
     if (!impl()->readFieldBegin(type, tag)) {
-      return NULL;
+      return nullptr;
     }
     if (type == T_STOP) {
       break;
@@ -860,7 +860,7 @@
     if (tag < 0 || tag >= spec_seq_len) {
       if (!skip(type)) {
         PyErr_SetString(PyExc_TypeError, "Error while skipping unknown field");
-        return NULL;
+        return nullptr;
       }
       continue;
     }
@@ -869,38 +869,38 @@
     if (item_spec == Py_None) {
       if (!skip(type)) {
         PyErr_SetString(PyExc_TypeError, "Error while skipping unknown field");
-        return NULL;
+        return nullptr;
       }
       continue;
     }
     StructItemSpec parsedspec;
     if (!parse_struct_item_spec(&parsedspec, item_spec)) {
-      return NULL;
+      return nullptr;
     }
     if (parsedspec.type != type) {
       if (!skip(type)) {
         PyErr_Format(PyExc_TypeError, "struct field had wrong type: expected %d but got %d",
                      parsedspec.type, type);
-        return NULL;
+        return nullptr;
       }
       continue;
     }
 
     ScopedPyObject fieldval(decodeValue(parsedspec.type, parsedspec.typeargs));
     if (!fieldval) {
-      return NULL;
+      return nullptr;
     }
 
     if ((immutable && PyDict_SetItem(kwargs.get(), parsedspec.attrname, fieldval.get()) == -1)
         || (!immutable && PyObject_SetAttr(output, parsedspec.attrname, fieldval.get()) == -1)) {
-      return NULL;
+      return nullptr;
     }
   }
   if (immutable) {
     ScopedPyObject args(PyTuple_New(0));
     if (!args) {
       PyErr_SetString(PyExc_TypeError, "failed to prepare argument storage");
-      return NULL;
+      return nullptr;
     }
     return PyObject_Call(klass, args.get(), kwargs.get());
   }
diff --git a/lib/py/src/ext/types.cpp b/lib/py/src/ext/types.cpp
index 68443fb..e8d6939 100644
--- a/lib/py/src/ext/types.cpp
+++ b/lib/py/src/ext/types.cpp
@@ -24,7 +24,7 @@
 namespace thrift {
 namespace py {
 
-PyObject* ThriftModule = NULL;
+PyObject* ThriftModule = nullptr;
 
 #if PY_MAJOR_VERSION < 3
 char refill_signature[] = {'s', '#', 'i'};
diff --git a/lib/py/src/ext/types.h b/lib/py/src/ext/types.h
index 5cd8dda..9b45dd0 100644
--- a/lib/py/src/ext/types.h
+++ b/lib/py/src/ext/types.h
@@ -83,7 +83,7 @@
 // replace with unique_ptr when we're OK with C++11
 class ScopedPyObject {
 public:
-  ScopedPyObject() : obj_(NULL) {}
+  ScopedPyObject() : obj_(nullptr) {}
   explicit ScopedPyObject(PyObject* py_object) : obj_(py_object) {}
   ~ScopedPyObject() {
     if (obj_)
@@ -98,7 +98,7 @@
   }
   PyObject* release() throw() {
     PyObject* tmp = obj_;
-    obj_ = NULL;
+    obj_ = nullptr;
     return tmp;
   }
   void swap(ScopedPyObject& other) throw() {