diff --git a/include/nod/Util.hpp b/include/nod/Util.hpp
index 6825070..69c649b 100644
--- a/include/nod/Util.hpp
+++ b/include/nod/Util.hpp
@@ -4,14 +4,8 @@
 #include <array>
 #include <cwctype>
 #include <direct.h>
-#ifndef WIN32_LEAN_AND_MEAN
-#define WIN32_LEAN_AND_MEAN 1
-#endif
-#ifndef NOMINMAX
-#define NOMINMAX
-#endif
 #include <nowide/stackstring.hpp>
-#include <windows.h>
+#include <winapifamily.h>
 #if defined(WINAPI_FAMILY) && WINAPI_FAMILY != WINAPI_FAMILY_DESKTOP_APP
 #define WINDOWS_STORE 1
 #else
@@ -181,32 +175,7 @@ static inline uint64_t SBig(uint64_t val) { return val; }
 #endif
 
 enum class FileLockType { None = 0, Read, Write };
-static inline FILE* Fopen(const char* path, const char* mode, FileLockType lock = FileLockType::None) {
-#if _MSC_VER
-  const nowide::wstackstring wpath(path);
-  const nowide::wshort_stackstring wmode(mode);
-  FILE* fp = _wfopen(wpath.get(), wmode.get());
-  if (!fp)
-    return nullptr;
-#else
-  FILE* fp = fopen(path, mode);
-  if (!fp)
-    return nullptr;
-#endif
-
-  if (lock != FileLockType::None) {
-#if _WIN32
-    OVERLAPPED ov = {};
-    LockFileEx((HANDLE)(uintptr_t)_fileno(fp), (lock == FileLockType::Write) ? LOCKFILE_EXCLUSIVE_LOCK : 0, 0, 0, 1,
-               &ov);
-#else
-    if (flock(fileno(fp), ((lock == FileLockType::Write) ? LOCK_EX : LOCK_SH) | LOCK_NB))
-      LogModule.report(logvisor::Error, FMT_STRING("flock {}: {}"), path, strerror(errno));
-#endif
-  }
-
-  return fp;
-}
+FILE* Fopen(const char* path, const char* mode, FileLockType lock = FileLockType::None);
 
 static inline int FSeek(FILE* fp, int64_t offset, int whence) {
 #if _WIN32
@@ -228,33 +197,6 @@ static inline int64_t FTell(FILE* fp) {
 #endif
 }
 
-static inline bool CheckFreeSpace(const char* path, size_t reqSz) {
-#if _WIN32
-  ULARGE_INTEGER freeBytes;
-  const nowide::wstackstring wpath(path);
-  std::array<wchar_t, 1024> buf{};
-  wchar_t* end = nullptr;
-  DWORD ret = GetFullPathNameW(wpath.get(), 1024, buf.data(), &end);
-  if (ret == 0 || ret > 1024) {
-    LogModule.report(logvisor::Error, FMT_STRING("GetFullPathNameW {}"), path);
-    return false;
-  }
-  if (end != nullptr) {
-    end[0] = L'\0';
-  }
-  if (!GetDiskFreeSpaceExW(buf.data(), &freeBytes, nullptr, nullptr)) {
-    LogModule.report(logvisor::Error, FMT_STRING("GetDiskFreeSpaceExW {}: {}"), path, GetLastError());
-    return false;
-  }
-  return reqSz < freeBytes.QuadPart;
-#else
-  struct statvfs svfs;
-  if (statvfs(path, &svfs)) {
-    LogModule.report(logvisor::Error, FMT_STRING("statvfs {}: {}"), path, strerror(errno));
-    return false;
-  }
-  return reqSz < svfs.f_frsize * svfs.f_bavail;
-#endif
-}
+bool CheckFreeSpace(const char* path, size_t reqSz);
 
 } // namespace nod
diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index 825b842..ed4277a 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -11,6 +11,7 @@ add_library(nod
   DiscWii.cpp
   nod.cpp
   OSUTF.c
+  Util.cpp
 
   ../include/nod/aes.hpp
   ../include/nod/DirectoryEnumerator.hpp
@@ -20,9 +21,9 @@ add_library(nod
   ../include/nod/IDiscIO.hpp
   ../include/nod/IFileIO.hpp
   ../include/nod/nod.hpp
+  ../include/nod/OSUTF.h
   ../include/nod/sha1.h
   ../include/nod/Util.hpp
-  ../include/nod/OSUTF.h
 )
 
 target_include_directories(nod PUBLIC
diff --git a/lib/FileIOWin32.cpp b/lib/FileIOWin32.cpp
index beece52..7841a55 100644
--- a/lib/FileIOWin32.cpp
+++ b/lib/FileIOWin32.cpp
@@ -1,7 +1,13 @@
-#include <cinttypes>
 #include <cstdint>
-#include <cstdio>
-#include <cstdlib>
+#if _WIN32
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN 1
+#endif
+#ifndef NOMINMAX
+#define NOMINMAX
+#endif
+#include <Windows.h>
+#endif
 
 #include "nod/IFileIO.hpp"
 #include "nod/Util.hpp"
diff --git a/lib/Util.cpp b/lib/Util.cpp
new file mode 100644
index 0000000..990b2e8
--- /dev/null
+++ b/lib/Util.cpp
@@ -0,0 +1,69 @@
+#include <nod/Util.hpp>
+
+#if _WIN32
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN 1
+#endif
+#ifndef NOMINMAX
+#define NOMINMAX
+#endif
+#include <Windows.h>
+#endif
+
+namespace nod {
+FILE* Fopen(const char* path, const char* mode, FileLockType lock) {
+#if _WIN32
+  const nowide::wstackstring wpath(path);
+  const nowide::wshort_stackstring wmode(mode);
+  FILE* fp = _wfopen(wpath.get(), wmode.get());
+  if (!fp)
+    return nullptr;
+#else
+  FILE* fp = fopen(path, mode);
+  if (!fp)
+    return nullptr;
+#endif
+
+  if (lock != FileLockType::None) {
+#if _WIN32
+    OVERLAPPED ov = {};
+    LockFileEx((HANDLE)(uintptr_t)_fileno(fp), (lock == FileLockType::Write) ? LOCKFILE_EXCLUSIVE_LOCK : 0, 0, 0, 1,
+               &ov);
+#else
+    if (flock(fileno(fp), ((lock == FileLockType::Write) ? LOCK_EX : LOCK_SH) | LOCK_NB))
+      LogModule.report(logvisor::Error, FMT_STRING("flock {}: {}"), path, strerror(errno));
+#endif
+  }
+
+  return fp;
+}
+
+bool CheckFreeSpace(const char* path, size_t reqSz) {
+#if _WIN32
+  ULARGE_INTEGER freeBytes;
+  const nowide::wstackstring wpath(path);
+  std::array<wchar_t, 1024> buf{};
+  wchar_t* end = nullptr;
+  DWORD ret = GetFullPathNameW(wpath.get(), 1024, buf.data(), &end);
+  if (ret == 0 || ret > 1024) {
+    LogModule.report(logvisor::Error, FMT_STRING("GetFullPathNameW {}"), path);
+    return false;
+  }
+  if (end != nullptr) {
+    end[0] = L'\0';
+  }
+  if (!GetDiskFreeSpaceExW(buf.data(), &freeBytes, nullptr, nullptr)) {
+    LogModule.report(logvisor::Error, FMT_STRING("GetDiskFreeSpaceExW {}: {}"), path, GetLastError());
+    return false;
+  }
+  return reqSz < freeBytes.QuadPart;
+#else
+  struct statvfs svfs;
+  if (statvfs(path, &svfs)) {
+    LogModule.report(logvisor::Error, FMT_STRING("statvfs {}: {}"), path, strerror(errno));
+    return false;
+  }
+  return reqSz < svfs.f_frsize * svfs.f_bavail;
+#endif
+}
+} // namespace nod