diff --git a/keyboards/1upkeyboards/1up60hse/rules.mk b/keyboards/1upkeyboards/1up60hse/rules.mk
index 3dcd689407aa..b166d77f065e 100644
--- a/keyboards/1upkeyboards/1up60hse/rules.mk
+++ b/keyboards/1upkeyboards/1up60hse/rules.mk
@@ -17,6 +17,6 @@ NKRO_ENABLE = yes            # USB Nkey Rollover
 BACKLIGHT_ENABLE = yes       # Enable keyboard backlight functionality
 RGBLIGHT_ENABLE = yes        # Enable keyboard RGB underglow
 AUDIO_ENABLE = no           # Audio output
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
 
 LAYOUTS = 60_ansi
diff --git a/keyboards/alf/x11/rules.mk b/keyboards/alf/x11/rules.mk
index 88daf0087296..b1232f5897bb 100644
--- a/keyboards/alf/x11/rules.mk
+++ b/keyboards/alf/x11/rules.mk
@@ -17,4 +17,4 @@ NKRO_ENABLE = no            # USB Nkey Rollover
 BACKLIGHT_ENABLE = yes       # Enable keyboard backlight functionality
 RGBLIGHT_ENABLE = yes        # Enable keyboard RGB underglow
 AUDIO_ENABLE = no           # Audio output
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
diff --git a/keyboards/cmm_studio/fuji65/rules.mk b/keyboards/cmm_studio/fuji65/rules.mk
index 0b27e9e3c335..2c83baeeea9c 100644
--- a/keyboards/cmm_studio/fuji65/rules.mk
+++ b/keyboards/cmm_studio/fuji65/rules.mk
@@ -17,6 +17,6 @@ NKRO_ENABLE = no            # USB Nkey Rollover
 BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
 RGBLIGHT_ENABLE = yes        # Enable keyboard RGB underglow
 AUDIO_ENABLE = no           # Audio output
-EXTRAFLAGS += -flto        # Use link time optimization
+LTO_ENABLE = yes            # Use link time optimization
 
 LAYOUTS = ortho_5x15
diff --git a/keyboards/converter/usb_usb/ble/rules.mk b/keyboards/converter/usb_usb/ble/rules.mk
index da45bc95284d..32ae864b424b 100644
--- a/keyboards/converter/usb_usb/ble/rules.mk
+++ b/keyboards/converter/usb_usb/ble/rules.mk
@@ -15,4 +15,4 @@ AUDIO_ENABLE = no           # Audio output
 BLUETOOTH = AdafruitBLE
 ADAFRUIT_BLE_ENABLE = yes
 
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
diff --git a/keyboards/hineybush/h87a/rules.mk b/keyboards/hineybush/h87a/rules.mk
index d4bab6bdb112..8f0c1ea107e0 100644
--- a/keyboards/hineybush/h87a/rules.mk
+++ b/keyboards/hineybush/h87a/rules.mk
@@ -17,4 +17,4 @@ NKRO_ENABLE = no            # USB Nkey Rollover
 BACKLIGHT_ENABLE = yes      # Enable keyboard backlight functionality
 RGBLIGHT_ENABLE = yes       # Enable RGB underglow
 AUDIO_ENABLE = no           # Audio output
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
diff --git a/keyboards/noxary/260/rules.mk b/keyboards/noxary/260/rules.mk
index d22906c6991f..285e65c53a7f 100644
--- a/keyboards/noxary/260/rules.mk
+++ b/keyboards/noxary/260/rules.mk
@@ -17,6 +17,6 @@ NKRO_ENABLE = no            # USB Nkey Rollover
 BACKLIGHT_ENABLE = yes       # Enable keyboard backlight functionality
 RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
 AUDIO_ENABLE = no           # Audio output
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
 
 LAYOUTS = 60_ansi 60_iso 60_hhkb 60_tsangan_hhkb
diff --git a/keyboards/percent/booster/rules.mk b/keyboards/percent/booster/rules.mk
index 40e9c81968c3..f53e944b1d7d 100644
--- a/keyboards/percent/booster/rules.mk
+++ b/keyboards/percent/booster/rules.mk
@@ -17,6 +17,6 @@ NKRO_ENABLE = no             # USB Nkey Rollover
 BACKLIGHT_ENABLE = yes       # Enable keyboard backlight functionality
 RGBLIGHT_ENABLE = yes        # Enable keyboard RGB underglow
 AUDIO_ENABLE = no            # Audio output
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes
 
 LAYOUTS = numpad_5x4
diff --git a/keyboards/tetris/rules.mk b/keyboards/tetris/rules.mk
index 65aca98cd340..7f5d2646bfc8 100755
--- a/keyboards/tetris/rules.mk
+++ b/keyboards/tetris/rules.mk
@@ -16,5 +16,5 @@ NKRO_ENABLE = yes		# USB Nkey Rollover - if this doesn't work, see here: https:/
 BACKLIGHT_ENABLE = no  # Enable keyboard backlight functionality
 AUDIO_ENABLE = yes
 RGBLIGHT_ENABLE = yes
-EXTRAFLAGS        = -flto 
+LTO_ENABLE = yes
 ENCODER_ENABLE = yes
diff --git a/keyboards/tkc/candybar/lefty/rules.mk b/keyboards/tkc/candybar/lefty/rules.mk
index e5930eb8290c..9f2ae0857006 100644
--- a/keyboards/tkc/candybar/lefty/rules.mk
+++ b/keyboards/tkc/candybar/lefty/rules.mk
@@ -7,7 +7,7 @@ BOOTLOADER = stm32-dfu
 # Build Options
 #   comment out to disable the options.
 #
-# EXTRAFLAGS+=-flto
+# LTO_ENABLE = yes
 LTO_ENABLE = yes
 BACKLIGHT_ENABLE = no
 BOOTMAGIC_ENABLE = yes      # Enable Bootmagic Lite
diff --git a/keyboards/tkc/candybar/righty/rules.mk b/keyboards/tkc/candybar/righty/rules.mk
index e5930eb8290c..9f2ae0857006 100644
--- a/keyboards/tkc/candybar/righty/rules.mk
+++ b/keyboards/tkc/candybar/righty/rules.mk
@@ -7,7 +7,7 @@ BOOTLOADER = stm32-dfu
 # Build Options
 #   comment out to disable the options.
 #
-# EXTRAFLAGS+=-flto
+# LTO_ENABLE = yes
 LTO_ENABLE = yes
 BACKLIGHT_ENABLE = no
 BOOTMAGIC_ENABLE = yes      # Enable Bootmagic Lite
diff --git a/keyboards/woodkeys/scarletbandana/rules.mk b/keyboards/woodkeys/scarletbandana/rules.mk
index 9cf0d600406e..2fc195a8e722 100644
--- a/keyboards/woodkeys/scarletbandana/rules.mk
+++ b/keyboards/woodkeys/scarletbandana/rules.mk
@@ -17,4 +17,4 @@ NKRO_ENABLE = no            # USB Nkey Rollover
 AUDIO_ENABLE = yes          # Audio output
 RGBLIGHT_ENABLE = yes       # Enable WS2812 RGB underlight.  Do not enable this with audio at the same time.
 BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality, also set ISSI_ENABLE below for Miera
-EXTRAFLAGS += -flto
+LTO_ENABLE = yes