diff --git a/ports/nrf/Makefile b/ports/nrf/Makefile
index 23be4430f..bc295cac8 100644
--- a/ports/nrf/Makefile
+++ b/ports/nrf/Makefile
@@ -138,12 +138,14 @@ LDFLAGS += -Wl,'--defsym=_fs_size=$(FS_SIZE)'
 endif
 
 #Debugging/Optimization
-CFLAGS += -g  # always include debug info in the ELF
 ifeq ($(DEBUG), 1)
 #ASMFLAGS += -g -gtabs+
-CFLAGS += -O0
+CFLAGS += -g -O0
 LDFLAGS += -O0
 else
+ifneq ($(LTO), 1)
+CFLAGS += -g  # always include debug info in the ELF, unless LTO is on
+endif
 CFLAGS += -Os -DNDEBUG
 LDFLAGS += -Os
 endif
diff --git a/ports/stm32/Makefile b/ports/stm32/Makefile
index 657524798..14a93a5aa 100644
--- a/ports/stm32/Makefile
+++ b/ports/stm32/Makefile
@@ -114,13 +114,15 @@ $(BUILD)/stm32_it.o $(BUILD)/pendsv.o: CFLAGS += -fno-lto
 endif
 
 # Debugging/Optimization
-CFLAGS += -g  # always include debug info in the ELF
 ifeq ($(DEBUG), 1)
-CFLAGS += -DPENDSV_DEBUG
+CFLAGS += -g -DPENDSV_DEBUG
 COPT ?= -Og
 # Disable text compression in debug builds
 MICROPY_ROM_TEXT_COMPRESSION = 0
 else
+ifneq ($(LTO), 1)
+CFLAGS += -g  # always include debug info in the ELF, unless LTO is on
+endif
 COPT ?= -Os -DNDEBUG
 endif