diff --git a/CMakeLists.txt b/CMakeLists.txt
index 725c3b4ae4593cfcf65e24d794eec9fd33ffe3a2..357b4059cf5c3b5c9878621485db1cd814eed1b4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,8 +11,10 @@ message("Using CMake ${CMAKE_VERSION}")
 # Set a flag for parallel compilation #
 #-------------------------------------#
 set(ENV{PARALLEL_BUILD_FLAG} "-j")
+set(PARALLEL_BUILD_FLAG $ENV{PARALLEL_BUILD_FLAG})
 if(WIN32)
     set(ENV{PARALLEL_BUILD_FLAG} "/MP")
+    set(PARALLEL_BUILD_FLAG $ENV{PARALLEL_BUILD_FLAG})
 endif()
 
 #------------------------------------------#
diff --git a/DownloadBoost.cmake b/DownloadBoost.cmake
index 194870fe6d0fa4affad1757e446d7b114127edd7..76fc5728bbcbd792400f98b811825935152fd0cf 100644
--- a/DownloadBoost.cmake
+++ b/DownloadBoost.cmake
@@ -40,7 +40,6 @@ FetchContent_Populate(boost)
 ###############
 # Build Boost #
 ###############
-
 set(BOOTSTRAP_CMD sh bootstrap.sh)
 set(B2_CMD ./b2 ${PARALLEL_BUILD_FLAG}${N_CORES})
 if(WIN32)