diff -urpN ir.lv2-1.3.4.orig/Makefile ir.lv2-1.3.4/Makefile
--- ir.lv2-1.3.4.orig/Makefile	2018-06-21 11:14:03.000000000 +0300
+++ ir.lv2-1.3.4/Makefile	2019-12-24 16:26:06.102495896 +0300
@@ -20,7 +20,7 @@ CC ?= gcc
 CXX ?= g++
 
 # change "-O2 -ffast-math" to "-g -O0" below if you want to debug the plugin
-CPPFLAGS += -Wall -I. -I/usr/include `pkg-config --cflags gtk+-2.0` `pkg-config --cflags gthread-2.0` -D__STDC_FORMAT_MACROS -O2 -ffast-math
+CPPFLAGS += -Wall -I. -I/usr/include `pkg-config --cflags gtk+-2.0` `pkg-config --cflags gthread-2.0` -D__STDC_FORMAT_MACROS -ffast-math
 LIBS += -lc -lm -lzita-convolver -lsamplerate -lsndfile `pkg-config --libs gthread-2.0` `pkg-config --libs gtk+-2.0`
 
 ifeq ($(shell pkg-config --atleast-version='2.16' gtk+-2.0; echo $$?), 1)
@@ -31,7 +31,7 @@ ifeq ($(shell pkg-config --atleast-versi
    CPPFLAGS += -D_HAVE_GTK_ATLEAST_2_20
 endif
 
-C4CFLAGS = -Wall -I. -I/usr/include `pkg-config --cflags gthread-2.0` -O2 -ffast-math
+C4CFLAGS = -Wall -I. -I/usr/include `pkg-config --cflags gthread-2.0` -ffast-math
 C4LIBS = -lsndfile `pkg-config --libs gthread-2.0`
 
 all: ir.so ir_gui.so