diff --git a/builders/windows-builder.py b/builders/windows-builder.py
index 07b9319..f9321df 100644
--- a/builders/windows-builder.py
+++ b/builders/windows-builder.py
@@ -267,7 +267,9 @@ class WindowsBuilder(Builder):
         super().setup_system_paths()
         self.python_root = os.path.dirname(self.python)
         self.site_packages = os.path.join(self.python_root, 'Lib', 'site-packages')
-        self.program_files = os.getenv('PROGRAMFILES')
+        self.program_files = os.getenv('PROGRAMFILES(x86)')
+        if not self.program_files:
+            self.program_files = os.getenv('PROGRAMFILES')
         self._print_verbose('   {:.<20}: {}'.format('site packages: ', self.site_packages))
         self._print_verbose('   {:.<20}: {}'.format('program files: ', self.program_files))