diff --git a/src/Makevars.win b/src/Makevars.win
index e3dac1c..d8d8d18 100755
--- a/src/Makevars.win
+++ b/src/Makevars.win
@@ -1,2 +1,3 @@
 ## Use the R_HOME indirection to support installations of multiple R version
-PKG_LIBS = $(shell $(R_HOME)/bin/Rscript.exe -e "Rcpp:::LdFlags()") $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS)
+PKG_CXXFLAGS = $(SHLIB_OPENMP_CXXFLAGS)
+PKG_LIBS = `$(R_HOME)/bin/Rscript.exe -e "Rcpp:::LdFlags()"` $(LAPACK_LIBS) $(BLAS_LIBS) $(FLIBS) $(SHLIB_OPENMP_CXXFLAGS)