diff --git a/Makefile b/Makefile
index c903d0017..8eca4bff4 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,7 @@ BOOTLOADER_BUILD_DIR=micropython/bootloader/build
 LOADER_BUILD_DIR=micropython/loader/build
 FIRMWARE_BUILD_DIR=micropython/firmware/build
 
-TREZORHAL_PORT_OPTS=FROZEN_MPY_DIR=src
+TREZORHAL_PORT_OPTS=FROZEN_MPY_DIR=src DEBUG=1
 UNIX_PORT_OPTS=MICROPY_FORCE_32BIT=1 MICROPY_PY_BTREE=0 MICROPY_PY_TERMIOS=0 MICROPY_PY_FFI=0 MICROPY_PY_USSL=0 MICROPY_SSL_AXTLS=0 DEBUG=1
 CROSS_PORT_OPTS=MICROPY_FORCE_32BIT=1
 
@@ -47,9 +47,6 @@ build: build_firmware build_bootloader build_loader build_unix build_cross ## bu
 build_firmware: vendor res build_cross ## build firmware with frozen modules
 	$(MAKE) -f Makefile.firmware $(TREZORHAL_PORT_OPTS)
 
-build_firmware_debug: vendor res build_cross ## build firmware with frozen modules and debug symbols
-	$(MAKE) -f Makefile.firmware $(TREZORHAL_PORT_OPTS) DEBUG=1
-
 build_bootloader: vendor ## build bootloader
 	$(MAKE) -f Makefile.bootloader $(TREZORHAL_PORT_OPTS)
 
diff --git a/Makefile.bootloader b/Makefile.bootloader
index a589a020c..7dd6feb0d 100644
--- a/Makefile.bootloader
+++ b/Makefile.bootloader
@@ -112,7 +112,7 @@ INC += -I$(SRCDIR_MP)/lib/cmsis/inc
 INC += -I$(BUILD)
 
 ifeq ($(DEBUG), 1)
-CFLAGS += -O0 -ggdb
+CFLAGS += -Os -ggdb
 else
 CFLAGS += -Os -DNDEBUG
 endif
diff --git a/Makefile.firmware b/Makefile.firmware
index 88766774d..005766cfd 100644
--- a/Makefile.firmware
+++ b/Makefile.firmware
@@ -360,7 +360,7 @@ INC += -I$(SRCDIR_MP)/lib/cmsis/inc
 INC += -I$(BUILD)
 
 ifeq ($(DEBUG), 1)
-CFLAGS += -O0 -ggdb
+CFLAGS += -Os -ggdb
 else
 CFLAGS += -Os -DNDEBUG
 endif
diff --git a/Makefile.loader b/Makefile.loader
index 8a671f26b..0c20b9ddc 100644
--- a/Makefile.loader
+++ b/Makefile.loader
@@ -110,7 +110,7 @@ INC += -I$(SRCDIR_MP)/lib/cmsis/inc
 INC += -I$(BUILD)
 
 ifeq ($(DEBUG), 1)
-CFLAGS += -O0 -ggdb
+CFLAGS += -Os -ggdb
 else
 CFLAGS += -Os -DNDEBUG
 endif
diff --git a/micropython/unix/Makefile b/micropython/unix/Makefile
index ed853614a..999be8f37 100644
--- a/micropython/unix/Makefile
+++ b/micropython/unix/Makefile
@@ -125,12 +125,12 @@ INC += -I$(BUILD)
 # compiler settings
 CWARN = -Wall -Werror
 CWARN += -Wpointer-arith -Wuninitialized
-CFLAGS = $(INC) $(CWARN) -ansi -std=gnu99 -DUNIX $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
+CFLAGS = $(INC) $(CWARN) -std=gnu99 -DUNIX $(CFLAGS_MOD) $(COPT) $(CFLAGS_EXTRA)
 
 # Debugging/Optimization
 ifdef DEBUG
 CFLAGS += -g
-COPT = -O0
+COPT = -Os
 else
 COPT = -Os -fdata-sections -ffunction-sections #-DNDEBUG
 # _FORTIFY_SOURCE is a feature in gcc/glibc which is intended to provide extra