diff --git a/Makefile b/Makefile
index 6c5ae89c..d64e504f 100644
--- a/Makefile
+++ b/Makefile
@@ -43,7 +43,7 @@ ifeq ($(MACHINE),PC)
 endif
 ifeq ($(MACHINE),DISCOVERER)
 	ifeq ($(FLAVOUR),GNU)
-		FC = h5pfc -cpp -fdefault-real-8 -fdefault-double-8
+		FC = h5pfc -O2 -cpp -fdefault-real-8 -fdefault-double-8
 		LDFLAGS += -lfftw3 -llapack -ldl
 	else
 		LDFLAGS += -lfftw3 -qmkl=sequential