diff --git a/build/toolchain.arm-gcc.mak b/build/toolchain.arm-gcc.mak
index 9bd156e6e..14995b2d1 100644
--- a/build/toolchain.arm-gcc.mak
+++ b/build/toolchain.arm-gcc.mak
@@ -5,18 +5,25 @@ GDB = arm-none-eabi-gdb
 OBJCOPY = arm-none-eabi-objcopy
 SIZE = arm-none-eabi-size
 
-LTO=1
-
-ifeq ($(DEBUG),1)
+# Always generate debug information
 SFLAGS += -ggdb3
+
+
+# LTO ?= NOT(DEBUG)
+ifeq ($(DEBUG),1)
+LTO ?= 0
 else
+LTO ?= 1
+endif
+
 ifeq ($(LTO),1)
+# Use link-time optimization if LTO=1
 SFLAGS += -flto
 else
+# Otherwise, just get rid of unused symbols
 SFLAGS += -fdata-sections -ffunction-sections
 LDFLAGS += -Wl,--gc-sections
 endif
-endif
 
 SFLAGS += -mthumb -march=armv7e-m -mfloat-abi=hard -mcpu=cortex-m4 -mfpu=fpv4-sp-d16
 LDFLAGS += $(SFLAGS) -lgcc -Wl,-T,$(LDSCRIPT)