diff --git a/build/cmake/DefinePlatformSpecifc.cmake b/build/cmake/DefinePlatformSpecifc.cmake
index 84409e6..a78d80c 100644
--- a/build/cmake/DefinePlatformSpecifc.cmake
+++ b/build/cmake/DefinePlatformSpecifc.cmake
@@ -25,8 +25,12 @@
 
 # basic options
 foreach(lang IN ITEMS C CXX)
-  if("CMAKE_${lang}_COMPILER_ID" STREQUAL "MSVC" OR "${CMAKE_${lang}_SIMULATE_ID}" STREQUAL "MSVC")
+  if("CMAKE_${lang}_COMPILER_ID" STREQUAL "MSVC")
+    # These flags are not supported (or needed) with Clang-Cl on Windows:
     set(CMAKE_${lang}_FLAGS "${CMAKE_${lang}_FLAGS} /MP") # parallel build
+  endif()
+
+  if("CMAKE_${lang}_COMPILER_ID" STREQUAL "MSVC" OR "${CMAKE_${lang}_SIMULATE_ID}" STREQUAL "MSVC")
     set(CMAKE_${lang}_FLAGS "${CMAKE_${lang}_FLAGS} /W3") # warning level 3
     include(CheckCXXCompilerFlag)
     set(CMAKE_REQUIRED_QUIET ON)