diff --git a/cmake/windows/buildspec.cmake b/cmake/windows/buildspec.cmake
index 75f2dca2..1b5a2f41 100644
--- a/cmake/windows/buildspec.cmake
+++ b/cmake/windows/buildspec.cmake
@@ -6,7 +6,11 @@ include(buildspec_common)
 
 # _check_dependencies_windows: Set up Windows slice for _check_dependencies
 function(_check_dependencies_windows)
-  set(arch ${CMAKE_GENERATOR_PLATFORM})
+  if(CMAKE_GENERATOR_PLATFORM)
+    set(arch ${CMAKE_GENERATOR_PLATFORM})
+  else()
+    set(arch x64)
+  endif()
   set(platform windows-${arch})
 
   set(dependencies_dir "${CMAKE_CURRENT_SOURCE_DIR}/.deps")