diff --git a/ports/atmel-samd/boards/arduino_mkr1300/mpconfigboard.mk b/ports/atmel-samd/boards/arduino_mkr1300/mpconfigboard.mk
index eda4d4d3e1..c3d75202bf 100644
--- a/ports/atmel-samd/boards/arduino_mkr1300/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/arduino_mkr1300/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_ONEWIREIO = 0
diff --git a/ports/atmel-samd/boards/arduino_mkrzero/mpconfigboard.mk b/ports/atmel-samd/boards/arduino_mkrzero/mpconfigboard.mk
index 2c8910a66a..eea3a27f13 100644
--- a/ports/atmel-samd/boards/arduino_mkrzero/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/arduino_mkrzero/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_ONEWIREIO = 0
diff --git a/ports/atmel-samd/boards/arduino_nano_33_iot/mpconfigboard.mk b/ports/atmel-samd/boards/arduino_nano_33_iot/mpconfigboard.mk
index 7fe396d698..38b1e96d6b 100644
--- a/ports/atmel-samd/boards/arduino_nano_33_iot/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/arduino_nano_33_iot/mpconfigboard.mk
@@ -10,4 +10,5 @@ INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
 
-CIRCUITPY_ONEWIREIO = 0
+# This board has many pins, and we have to remove something else to make room.
+CIRCUITPY_RAINBOWIO = 0
diff --git a/ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk b/ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk
index f1c3631dcb..5ee22c59ad 100644
--- a/ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/arduino_zero/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_ONEWIREIO = 0
diff --git a/ports/atmel-samd/boards/circuitplayground_express_crickit/mpconfigboard.mk b/ports/atmel-samd/boards/circuitplayground_express_crickit/mpconfigboard.mk
index 4d749d2134..fb65d7cd0a 100644
--- a/ports/atmel-samd/boards/circuitplayground_express_crickit/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/circuitplayground_express_crickit/mpconfigboard.mk
@@ -15,7 +15,6 @@ LONGINT_IMPL = NONE
 CIRCUITPY_BUSDEVICE = 1
 CIRCUITPY_DISPLAYIO = 0
 CIRCUITPY_KEYPAD = 0
-CIRCUITPY_ONEWIREIO = 0
 
 # Include these Python libraries in firmware.
 FROZEN_MPY_DIRS += $(TOP)/frozen/Adafruit_CircuitPython_CircuitPlayground
diff --git a/ports/atmel-samd/boards/datum_imu/mpconfigboard.mk b/ports/atmel-samd/boards/datum_imu/mpconfigboard.mk
index 90076481da..9c3b642330 100644
--- a/ports/atmel-samd/boards/datum_imu/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/datum_imu/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_ONEWIREIO = 0
diff --git a/ports/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.mk b/ports/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.mk
index e17cb8b3a1..62336ecf50 100644
--- a/ports/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/feather_m0_adalogger/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_ONEWIREIO = 0
diff --git a/ports/atmel-samd/boards/seeeduino_xiao/mpconfigboard.mk b/ports/atmel-samd/boards/seeeduino_xiao/mpconfigboard.mk
index 676f2bca3a..1334c8312c 100644
--- a/ports/atmel-samd/boards/seeeduino_xiao/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/seeeduino_xiao/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_ONEWIREIO = 0
diff --git a/ports/atmel-samd/boards/sensebox_mcu/mpconfigboard.mk b/ports/atmel-samd/boards/sensebox_mcu/mpconfigboard.mk
index f59483a608..568503afe9 100644
--- a/ports/atmel-samd/boards/sensebox_mcu/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/sensebox_mcu/mpconfigboard.mk
@@ -11,6 +11,4 @@ LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
 
 # There are many pin definitions on this board; it doesn't quite fit on very large translations.
-# Remove a couple of modules.
-CIRCUITPY_ONEWIREIO = 0
 CIRCUITPY_RAINBOWIO = 0
diff --git a/ports/atmel-samd/boards/sparkfun_samd21_dev/mpconfigboard.mk b/ports/atmel-samd/boards/sparkfun_samd21_dev/mpconfigboard.mk
index 8d1de11be7..b8ac2dc256 100644
--- a/ports/atmel-samd/boards/sparkfun_samd21_dev/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/sparkfun_samd21_dev/mpconfigboard.mk
@@ -9,5 +9,3 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
-
-CIRCUITPY_ONEWIREIO = 0
diff --git a/ports/atmel-samd/boards/stringcar_m0_express/mpconfigboard.mk b/ports/atmel-samd/boards/stringcar_m0_express/mpconfigboard.mk
index 8274c71243..706797928e 100644
--- a/ports/atmel-samd/boards/stringcar_m0_express/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/stringcar_m0_express/mpconfigboard.mk
@@ -12,7 +12,6 @@ EXTERNAL_FLASH_DEVICES = AT25SF161
 LONGINT_IMPL = MPZ
 
 CIRCUITPY_KEYPAD = 0
-CIRCUITPY_ONEWIREIO = 0
 CIRCUITPY_USB_MIDI = 0
 
 CIRCUITPY_BITBANG_APA102 = 1
diff --git a/ports/atmel-samd/mpconfigport.mk b/ports/atmel-samd/mpconfigport.mk
index 9ba16321ca..82cc69728a 100644
--- a/ports/atmel-samd/mpconfigport.mk
+++ b/ports/atmel-samd/mpconfigport.mk
@@ -47,6 +47,14 @@ CIRCUITPY_TOUCHIO_USE_NATIVE ?= 1
 CIRCUITPY_ULAB = 0
 CIRCUITPY_VECTORIO = 0
 
+# TODO: In CircuitPython 8.0, turn this back on, after `busio.OneWire` is removed.
+# We'd like a smoother transition, but we can't afford the space to have both
+# `busio.OneWire` and `onewireio.OneWire` present on these tiny builds.
+
+ifeq ($(INTERNAL_FLASH_FILESYSTEM),1)
+CIRCUITPY_ONEWIREIO ?= 0
+endif
+
 MICROPY_PY_ASYNC_AWAIT = 0
 
 # We don't have room for the fonts for terminalio for ja and ko