diff --git a/GNUmakefile b/GNUmakefile
index 35416e7b..e680e8f3 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -21,7 +21,7 @@ suffix  ?=
 CC      ?= gcc
 LD      ?= ld
 MDBX_OPTIONS ?= -DNDEBUG=1
-CFLAGS  ?= -O2 -g3 -Wall -Werror -Wextra -ffunction-sections -fPIC -fvisibility=hidden -std=gnu11 -pthread
+CFLAGS  ?= -Os -g3 -Wall -Werror -Wextra -ffunction-sections -fPIC -fvisibility=hidden -std=gnu11 -pthread
 
 # LY: '--no-as-needed,-lrt' for ability to built with modern glibc, but then run with the old
 LDFLAGS ?= $(shell $(LD) --help 2>/dev/null | grep -q -- --gc-sections && echo '-Wl,--gc-sections,-z,relro,-O1')$(shell $(LD) --help 2>/dev/null | grep -q -- -dead_strip && echo '-Wl,-dead_strip')