diff --git a/Windows/winunwind.cpp b/Windows/winunwind.cpp
index e550957..0870698 100644
--- a/Windows/winunwind.cpp
+++ b/Windows/winunwind.cpp
@@ -1,3 +1,21 @@
+/*
+Copyright 2021 Google LLC
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+https ://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+#ifdef _WIN64
+
 #include "winunwind.h"
 
 WinUnwindData::~WinUnwindData() {
@@ -674,4 +692,6 @@ void WinUnwindGenerator::OnBasicBlockEnd(ModuleInfo* module,
   WinUnwindData* unwind_data = (WinUnwindData*)module->unwind_data;
   if (unwind_data->last_translated_entry) 
     unwind_data->last_translated_entry->function_end = translated_address;
-}
\ No newline at end of file
+}
+
+#endif // _WIN64
diff --git a/Windows/winunwind.h b/Windows/winunwind.h
index a592189..865e624 100644
--- a/Windows/winunwind.h
+++ b/Windows/winunwind.h
@@ -1,7 +1,24 @@
+/*
+Copyright 2021 Google LLC
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+https ://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
 
 #ifndef WINUNWIND_H
 #define WINUNWIND_H
 
+#ifdef _WIN64
+
 #include "unwind.h"
 #include "tinyinst.h"
 
@@ -146,4 +163,6 @@ class WinUnwindGenerator : public UnwindGenerator {
 	size_t RtlAddFunctionTable_addr;
 };
 
+#endif // _WIN64
+
 #endif // WINUNWIND_H
diff --git a/tinyinst.cpp b/tinyinst.cpp
index 2c5cf77..c9630e9 100644
--- a/tinyinst.cpp
+++ b/tinyinst.cpp
@@ -1174,7 +1174,7 @@ void TinyInst::Init(int argc, char **argv) {
   } else {
 #ifdef __APPLE__
     unwind_generator = new UnwindGeneratorMacOS(*this);
-#elif defined(WIN32) || defined(_WIN32) || defined(__WIN32)
+#elif defined(_WIN64)
     unwind_generator = new WinUnwindGenerator(*this);
 #else
     WARN("Unwind generator not implemented for the current platform");
diff --git a/tinyinst.h b/tinyinst.h
index 23feb38..7e93a8b 100644
--- a/tinyinst.h
+++ b/tinyinst.h
@@ -33,7 +33,7 @@ limitations under the License.
 #include "instruction.h"
 #include "unwind.h"
 
-#if defined(WIN32) || defined(_WIN32) || defined(__WIN32)
+#if defined(_WIN64)
 
 #include "Windows/winunwind.h"
 
@@ -243,7 +243,7 @@ class TinyInst : public Debugger {
   friend class Arm64Assembler;
   friend class ModuleInfo;
   friend class UnwindGenerator;
-#if defined(WIN32) || defined(_WIN32) || defined(__WIN32)
+#if defined(_WIN64)
   friend class WinUnwindGenerator;
 #elif __APPLE__
   friend class UnwindGeneratorMacOS;