diff --git a/bypy/windows/portable-installer.cpp b/bypy/windows/portable-installer.cpp
index e695f43382..5244bc9d30 100644
--- a/bypy/windows/portable-installer.cpp
+++ b/bypy/windows/portable-installer.cpp
@@ -526,7 +526,7 @@ int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, PWSTR pCmdLine
     WCHAR buf[4*MAX_PATH] = {0}, mb_msg[4*MAX_PATH] = {0}, fdest[4*MAX_PATH] = {0};
 
     if (!load_data(&cdata, &csz)) return ret;
-    if (!IsWindows10OrGreater()) { show_error(L"Your version of Windows is tool old. calibre requires Windows 10 or greater."); return ret; }
+    if (!IsWindows10OrGreater()) { show_error(L"Your version of Windows is too old. calibre requires Windows 10 or greater."); return ret; }
 
     hr = CoInitialize(NULL);
     if (FAILED(hr)) { show_error(L"Failed to initialize COM"); return ret; }