--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -61,7 +61,6 @@ str_test_CPPFLAGS= -I$(top_builddir)/include/ -I$(top_srcdir)/include/
 str_test_LDADD= -lpthread ../src/libcdada.la
 
 benchmark_SOURCES= benchmark.cc
-benchmark_CXXFLAGS= -O3
 benchmark_CPPFLAGS= -I$(top_builddir)/include/ -I$(top_srcdir)/include/
 benchmark_LDADD= -lpthread ../src/.libs/libcdada.a
 
--- a/config_m4/debug.m4
+++ b/config_m4/debug.m4
@@ -10,8 +10,8 @@
 	AC_DEFINE([DEBUG], [], [Description])
 	AC_MSG_RESULT(yes)
 else
-	CFLAGS="$CFLAGS -O3" #--compiler-options -fno-strict-aliasing --compiler-options -fno-inline
-	CXXFLAGS="$CXXFLAGS -O3" #-fomit-frame-pointer"
+	CFLAGS="$CFLAGS" #--compiler-options -fno-strict-aliasing --compiler-options -fno-inline
+	CXXFLAGS="$CXXFLAGS" #-fomit-frame-pointer"
 	AC_DEFINE([NDEBUG], [], [Description])
 	AC_MSG_RESULT(no)
 fi