diff --git a/cmake/MpcOptions.cmake b/cmake/MpcOptions.cmake
index 0fe3e1bf7..ec71f592b 100644
--- a/cmake/MpcOptions.cmake
+++ b/cmake/MpcOptions.cmake
@@ -103,7 +103,8 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR (CMAKE_CXX_COMPILER_ID MATCHES "Clang
   endif()
 endif()
 
-if(NOT CMAKE_INTERPROCEDURAL_OPTIMIZATION AND (CMAKE_BUILD_TYPE AND NOT CMAKE_BUILD_TYPE STREQUAL "Debug"))
+if(NOT DEFINED CMAKE_INTERPROCEDURAL_OPTIMIZATION AND
+   (CMAKE_BUILD_TYPE AND NOT CMAKE_BUILD_TYPE STREQUAL "Debug"))
   set(CMAKE_INTERPROCEDURAL_OPTIMIZATION ON)
 endif()