diff --git a/source/CMakeLists.txt b/source/CMakeLists.txt
index 79a81a1..fa900e0 100644
--- a/source/CMakeLists.txt
+++ b/source/CMakeLists.txt
@@ -414,7 +414,7 @@
   install(FILES ${CMAKE_BINARY_DIR}/${SPIRV_TOOLS}Config.cmake DESTINATION ${PACKAGE_DIR})
 endif(ENABLE_SPIRV_TOOLS_INSTALL)
 
-if(MSVC)
+if(MSVC AND (NOT ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")))
   # Enable parallel builds across four cores for this lib
   add_definitions(/MP4)
 endif()
diff --git a/source/fuzz/CMakeLists.txt b/source/fuzz/CMakeLists.txt
index a056630..2cef37b 100644
--- a/source/fuzz/CMakeLists.txt
+++ b/source/fuzz/CMakeLists.txt
@@ -304,7 +304,7 @@
         ${CMAKE_CURRENT_BINARY_DIR}/protobufs/spvtoolsfuzz.pb.cc
         )
 
-  if(MSVC)
+  if(MSVC AND (NOT ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")))
     # Enable parallel builds across four cores for this lib
     add_definitions(/MP4)
   endif()
diff --git a/source/opt/CMakeLists.txt b/source/opt/CMakeLists.txt
index 090aeac..3630a06 100644
--- a/source/opt/CMakeLists.txt
+++ b/source/opt/CMakeLists.txt
@@ -226,7 +226,7 @@
   wrap_opkill.cpp
 )
 
-if(MSVC)
+if(MSVC AND (NOT ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")))
   # Enable parallel builds across four cores for this lib
   add_definitions(/MP4)
 endif()
diff --git a/source/reduce/CMakeLists.txt b/source/reduce/CMakeLists.txt
index 865510b..9480a43 100644
--- a/source/reduce/CMakeLists.txt
+++ b/source/reduce/CMakeLists.txt
@@ -70,7 +70,7 @@
         simple_conditional_branch_to_branch_reduction_opportunity.cpp
 )
 
-if(MSVC)
+if(MSVC AND (NOT ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")))
   # Enable parallel builds across four cores for this lib
   add_definitions(/MP4)
 endif()