diff --git a/installation/windows/install_fortran.bat b/installation/windows/install_fortran.bat
index bad34b7..c03714c 100644
--- a/installation/windows/install_fortran.bat
+++ b/installation/windows/install_fortran.bat
@@ -128,7 +128,7 @@ ECHO FT_00_LB=_Compile >> "filetypes.fortran"
 ECHO FT_00_CM=gfortran -O3 -Wno-unused -frecursive -ffree-line-length-none -fopenmp -fimplicit-none -Wall -fcheck=bound,do -ffpe-trap=invalid,zero,overflow -I"%locnew%\\include" -c "%%f" -o "%%e.o" >> "filetypes.fortran"
 ECHO FT_00_WD= >> "filetypes.fortran"
 ECHO FT_01_LB=_Build >> "filetypes.fortran"
-ECHO FT_01_CM=gfortran -O3 "%locnew%\\include\\toolbox.o" "%%e.o" -o prog >> "filetypes.fortran"
+ECHO FT_01_CM=gfortran -O3 -fopenmp "%locnew%\\include\\toolbox.o" "%%e.o" -o prog >> "filetypes.fortran"
 ECHO FT_01_WD= >> "filetypes.fortran"
 ECHO FT_02_LB=_Debug >> "filetypes.fortran"
 ECHO FT_02_CM=gfortran -Wno-unused -frecursive -ffree-line-length-none -fopenmp -fimplicit-none -Wall -fcheck=bound,do -ffpe-trap=invalid,zero,overflow -I"%locnew%\\include" -g "%%f" -o "%%e.o" "%locnew%\\include\\toolbox_debug.o" >> "filetypes.fortran"