diff --git a/FFXIVLauncher/Login.cpp b/FFXIVLauncher/Login.cpp
index 0a4b0ce..468ed83 100644
--- a/FFXIVLauncher/Login.cpp
+++ b/FFXIVLauncher/Login.cpp
@@ -328,6 +328,22 @@ static void EncodeFormURIComponent(std::ostream & output, char c)
 }
 
 bool HashFile(std::ostream & output, const fs::path & path)
+{
+    byte buf[160 / 8];
+    HashFile(buf, path);
+
+    output << fs::file_size(path) << '/';
+    output << std::hex;
+    for (size_t i = 0; i < 160 / 8; i++)
+    {
+        output << std::setfill('0') << std::setw(2) << (uint32_t)buf[i];
+    }
+    output << std::dec;
+
+    return true;
+}
+
+bool HashFile(byte(&output)[160 / 8], const fs::path & path)
 {
     HCRYPTPROV hProv = 0;
     HCRYPTHASH hHash = 0;
@@ -360,17 +376,8 @@ bool HashFile(std::ostream & output, const fs::path & path)
         return false;
     }
 
-    numread = 160 / 8;
-    CryptGetHashParam(hHash, HP_HASHVAL, buf, &numread, 0);
-
-    output << fs::file_size(path) << '/';
-    output << std::hex;
-    for (size_t i = 0; i < numread; i++)
-    {
-        output << std::setfill('0') << std::setw(2) << (uint32_t)buf[i];
-    }
-    output << std::dec;
-
+    numread = sizeof(output);
+    CryptGetHashParam(hHash, HP_HASHVAL, output, &numread, 0);
     return true;
 }
 
diff --git a/FFXIVLauncher/Login.h b/FFXIVLauncher/Login.h
index 9baae08..b883280 100644
--- a/FFXIVLauncher/Login.h
+++ b/FFXIVLauncher/Login.h
@@ -14,3 +14,25 @@ LoginResult PerformLogin();
 void LaunchGame();
 void LaunchUpdater();
 bool BootWasReplaced();
+
+
+bool HashFile(byte(&buf)[160 / 8], const fs::path &path);
+
+struct FileHash { byte buf[160 / 8]; };
+inline std::optional<FileHash> HashFile(const fs::path &path)
+{
+    FileHash hash;
+    if (!HashFile(hash.buf, path))
+        return {};
+    return hash;
+}
+
+inline bool operator==(const FileHash &lhs, const FileHash &rhs)
+{
+    return memcmp(lhs.buf, rhs.buf, sizeof(lhs.buf)) == 0;
+}
+
+inline bool operator!=(const FileHash &lhs, const FileHash &rhs)
+{
+    return !(lhs == rhs);
+}
diff --git a/FFXIVLauncher/LoginDialog.cpp b/FFXIVLauncher/LoginDialog.cpp
index 1cb92fe..7dfd2bd 100644
--- a/FFXIVLauncher/LoginDialog.cpp
+++ b/FFXIVLauncher/LoginDialog.cpp
@@ -156,9 +156,9 @@ static void InitializeUI(HWND dialog) noexcept
 
     if (self_path != boot)
     {
-        auto selfsize = fs::file_size(self_path);
-        auto bootsize = fs::file_size(boot);
-        if (selfsize != bootsize)
+        auto selfhash = HashFile(self_path);
+        auto boothash = HashFile(boot);
+        if (selfhash != boothash)
         {
             auto hInstall = GetDlgItem(dialog, IDC_INSTALLBTN);
             auto style = GetWindowLongW(hInstall, GWL_STYLE);