diff --git a/keyboards/contra/keymaps/maxr1998/rules.mk b/keyboards/contra/keymaps/maxr1998/rules.mk
index e1ba074290b..8607ce19ef7 100644
--- a/keyboards/contra/keymaps/maxr1998/rules.mk
+++ b/keyboards/contra/keymaps/maxr1998/rules.mk
@@ -1,7 +1,7 @@
 RGBLIGHT_ENABLE = yes
 KEY_LOCK_ENABLE = yes
 
-EXTRAFLAGS      += -flto
+LTO_ENABLE      = yes
 UNICODE_ENABLE  = no
 MOUSEKEY_ENABLE = no
 
diff --git a/keyboards/crkbd/keymaps/snowe/rules.mk b/keyboards/crkbd/keymaps/snowe/rules.mk
index ce3b5928fad..96ae4bbf95f 100644
--- a/keyboards/crkbd/keymaps/snowe/rules.mk
+++ b/keyboards/crkbd/keymaps/snowe/rules.mk
@@ -21,6 +21,6 @@ OCEAN_DREAM_ENABLE = yes
 LUNA_ENABLE = no # disabled so travis build succeeds
 
 # if firmware size over limit, try this option
-CFLAGS += -flto
+LTO_ENABLE = yes
 
 WPM_ENABLE = yes
diff --git a/keyboards/dztech/dz60rgb/keymaps/matthewrobo/rules.mk b/keyboards/dztech/dz60rgb/keymaps/matthewrobo/rules.mk
index 15b8ec1bafc..e2618e52906 100644
--- a/keyboards/dztech/dz60rgb/keymaps/matthewrobo/rules.mk
+++ b/keyboards/dztech/dz60rgb/keymaps/matthewrobo/rules.mk
@@ -2,6 +2,6 @@ NKRO_ENABLE = yes                 # USB Nkey Rollover
 AUTO_SHIFT_ENABLE = yes      # Auto Shift
 # VELOCIKEY_ENABLE = yes
 
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
 
 # SRC += dz60rgb.c
diff --git a/keyboards/dztech/dz65rgb/keymaps/drootz/rules.mk b/keyboards/dztech/dz65rgb/keymaps/drootz/rules.mk
index 24a765ab9a0..2f8ab8ecc38 100644
--- a/keyboards/dztech/dz65rgb/keymaps/drootz/rules.mk
+++ b/keyboards/dztech/dz65rgb/keymaps/drootz/rules.mk
@@ -2,7 +2,7 @@ DYNAMIC_MACRO_ENABLE = yes
 LEADER_ENABLE = yes
 
 # Firmware size Optimizations
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
 MOUSEKEY_ENABLE = no
 NKRO_ENABLE = no
 SPACE_CADET_ENABLE = no
diff --git a/keyboards/handwired/dactyl_manuform/5x6/keymaps/333fred/rules.mk b/keyboards/handwired/dactyl_manuform/5x6/keymaps/333fred/rules.mk
index 6d2e27cb41c..5ad63b02b70 100644
--- a/keyboards/handwired/dactyl_manuform/5x6/keymaps/333fred/rules.mk
+++ b/keyboards/handwired/dactyl_manuform/5x6/keymaps/333fred/rules.mk
@@ -1,3 +1,3 @@
 KEY_LOCK_ENABLE = yes
 CONSOLE_ENABLE = no
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
diff --git a/keyboards/keebio/iris/keymaps/333fred/rules.mk b/keyboards/keebio/iris/keymaps/333fred/rules.mk
index 995272e2f22..5ad63b02b70 100644
--- a/keyboards/keebio/iris/keymaps/333fred/rules.mk
+++ b/keyboards/keebio/iris/keymaps/333fred/rules.mk
@@ -1,4 +1,3 @@
 KEY_LOCK_ENABLE = yes
 CONSOLE_ENABLE = no
-EXTRAFLAGS += -flto
-
+LTO_ENABLE = yes
diff --git a/keyboards/lily58/keymaps/druotoni/rules.mk b/keyboards/lily58/keymaps/druotoni/rules.mk
index c07761108ea..b3182cb46af 100644
--- a/keyboards/lily58/keymaps/druotoni/rules.mk
+++ b/keyboards/lily58/keymaps/druotoni/rules.mk
@@ -9,7 +9,6 @@ BOOTLOADER = atmel-dfu
 
 # Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
 SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend
-# EXTRAFLAGS += -flto
 LTO_ENABLE = yes
 SPACE_CADET_ENABLE = no
 GRAVE_ESC_ENABLE = no
diff --git a/keyboards/rgbkb/zen/rev1/keymaps/333fred/rules.mk b/keyboards/rgbkb/zen/rev1/keymaps/333fred/rules.mk
index f858bbe3daa..a5b44540736 100644
--- a/keyboards/rgbkb/zen/rev1/keymaps/333fred/rules.mk
+++ b/keyboards/rgbkb/zen/rev1/keymaps/333fred/rules.mk
@@ -1,4 +1,4 @@
 RGBLIGHT_ENABLE = yes
 KEY_LOCK_ENABLE = yes
 CONSOLE_ENABLE = no
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
diff --git a/keyboards/rgbkb/zygomorph/keymaps/kageurufu/rules.mk b/keyboards/rgbkb/zygomorph/keymaps/kageurufu/rules.mk
index d484c473669..c5cc34d8989 100644
--- a/keyboards/rgbkb/zygomorph/keymaps/kageurufu/rules.mk
+++ b/keyboards/rgbkb/zygomorph/keymaps/kageurufu/rules.mk
@@ -41,4 +41,4 @@ ifeq ($(strip $(RGBLIGHT_SPLIT_ENABLE)), yes)
 endif
 
 # Link time optimization, should save on firmware size
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
diff --git a/keyboards/woodkeys/meira/keymaps/cole/rules.mk b/keyboards/woodkeys/meira/keymaps/cole/rules.mk
index 8f8d53e57a5..eed6b9c1190 100644
--- a/keyboards/woodkeys/meira/keymaps/cole/rules.mk
+++ b/keyboards/woodkeys/meira/keymaps/cole/rules.mk
@@ -1,2 +1,2 @@
 AUDIO_ENABLE = yes           # Audio output on port C6
-EXTRAFLAGS+=-flto # -4-7k
\ No newline at end of file
+LTO_ENABLE = yes # -4-7k
diff --git a/keyboards/woodkeys/meira/keymaps/grahampheath/rules.mk b/keyboards/woodkeys/meira/keymaps/grahampheath/rules.mk
index b3b1980eb15..1c61fe1c12b 100644
--- a/keyboards/woodkeys/meira/keymaps/grahampheath/rules.mk
+++ b/keyboards/woodkeys/meira/keymaps/grahampheath/rules.mk
@@ -1,5 +1,5 @@
 AUDIO_ENABLE = yes           # Audio output on port C6
-EXTRAFLAGS+=-flto # -4-7k
+LTO_ENABLE = yes # -4-7k
 MOUSEKEY_ENABLE = no       # Mouse keys(-47kb)
 ISSI_ENABLE = no
 BACKLIGHT_ENABLE = no
\ No newline at end of file
diff --git a/keyboards/yoichiro/lunakey_mini/keymaps/via/rules.mk b/keyboards/yoichiro/lunakey_mini/keymaps/via/rules.mk
index 8b55a3b731f..989d0d173c5 100644
--- a/keyboards/yoichiro/lunakey_mini/keymaps/via/rules.mk
+++ b/keyboards/yoichiro/lunakey_mini/keymaps/via/rules.mk
@@ -2,4 +2,4 @@ RGBLIGHT_ENABLE = yes        # Enable keyboard RGB Underglow
 AUDIO_ENABLE = no            # Enable Audio output
 OLED_ENABLE = no      # Enable OLED Display
 VIA_ENABLE = yes             # Enable VIA support
-LTO_ENABLE = yes             # CFLAGS=flto
+LTO_ENABLE = yes             # Reduce firmware size