--- a/Makefile
+++ b/Makefile
@@ -28,10 +28,8 @@ makefiles = \
 OPTIMIZE = 1
 
 ifeq ($(OPTIMIZE), 1)
-  GLOBAL_CXXFLAGS += -O3 $(CXXLTO)
+  GLOBAL_CXXFLAGS += $(CXXLTO)
   GLOBAL_LDFLAGS += $(CXXLTO)
-else
-  GLOBAL_CXXFLAGS += -O0 -U_FORTIFY_SOURCE
 endif
 
 include mk/lib.mk
--- a/configure.ac
+++ b/configure.ac
@@ -41,8 +41,6 @@ AC_DEFINE_UNQUOTED(SYSTEM, ["$system"],
 test "$localstatedir" = '${prefix}/var' && localstatedir=/nix/var
 
 
-CFLAGS=
-CXXFLAGS=
 AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_CPP
