diff --git a/Makefile b/Makefile
index e3e90a0..62e24f7 100644
--- a/Makefile
+++ b/Makefile
@@ -66,7 +66,7 @@ GIT_DIRTY ?= $(shell test -n "$$(git status --porcelain)" && echo "-dirty")
 # Note: can't use ?= for FC because GNU Make defaults to f77
 FC        = gfortran
 LD        = gfortran
-FFLAGS   += -O3 -J$(OBJDIR) -I$(INCDIR) -ffree-line-length-none -fPIC
+FFLAGS   += -J$(OBJDIR) -I$(INCDIR) -ffree-line-length-none -fPIC
 CPPFLAGS += -DREVISION=\"$(GIT_REV)$(GIT_DIRTY)\" -DPREFIX=\"$(PREFIX)\"
 
 # Static build options
@@ -80,6 +80,9 @@ ifdef DEBUG
 FFLAGS += -ggdb -O0 -Wall -Wunused-parameter
 # Tricks to detect uninitialised memory
 FFLAGS += -finit-integer=7777777 -finit-real=snan -ffpe-trap=invalid
+else
+# Optimization level 3
+FFLAGS += -O3
 endif
 
 ##