diff --git a/lib/g4.bat b/lib/g4.bat
index c5eb936d4..6475dad78 100644
--- a/lib/g4.bat
+++ b/lib/g4.bat
@@ -1,3 +1,3 @@
 gcc -c gran.c
-gfortran -c fftw3mod.f90
-gfortran -o timefft timefft.f90 timefft_opts.f90 gran.o libfftw3f-3.dll
+gfortran -c -Wall fftw3mod.f90
+gfortran -o timefft -Wall timefft.f90 timefft_opts.f90 gran.o libfftw3f-3.dll