diff --git a/src/Makevars.ucrt b/src/Makevars.ucrt
new file mode 100644
index 00000000..3a7f8ac9
--- /dev/null
+++ b/src/Makevars.ucrt
@@ -0,0 +1,2 @@
+PKG_CXXFLAGS = $(SHLIB_OPENMP_CXXFLAGS)
+PKG_LIBS = $(SHLIB_OPENMP_CXXFLAGS) $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)
diff --git a/src/Makevars.win b/src/Makevars.win
index 6660c7f9..d345aec8 100644
--- a/src/Makevars.win
+++ b/src/Makevars.win
@@ -1,3 +1,5 @@
+# This file will only be used on R < 4.2.
+# Newer versions of R will prefer Makevars.ucrt
 CXX_STD = CXX14
 PKG_CXXFLAGS = $(SHLIB_OPENMP_CXXFLAGS)
 PKG_LIBS = $(SHLIB_OPENMP_CXXFLAGS) $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)