diff --git a/ports/atmel-samd/mpconfigport.mk b/ports/atmel-samd/mpconfigport.mk
index 8958550060..df108664ad 100644
--- a/ports/atmel-samd/mpconfigport.mk
+++ b/ports/atmel-samd/mpconfigport.mk
@@ -38,6 +38,8 @@ ifeq ($(CHIP_FAMILY),samd51)
 # No native touchio on SAMD51.
 CIRCUITPY_TOUCHIO_USE_NATIVE = 0
 
+# The ifndef's allow overriding in mpconfigboard.mk.
+
 ifndef CIRCUITPY_NETWORK
 CIRCUITPY_NETWORK = 1
 MICROPY_PY_WIZNET5K = 5500
diff --git a/ports/nrf/mpconfigport.mk b/ports/nrf/mpconfigport.mk
index d070978b71..f61d9f8eae 100644
--- a/ports/nrf/mpconfigport.mk
+++ b/ports/nrf/mpconfigport.mk
@@ -17,6 +17,8 @@ endif
 
 CIRCUITPY_AUDIOIO = 0
 
+# The ifndef's allow overriding in mpconfigboard.mk.
+
 ifndef CIRCUITPY_AUDIOMIXER
 CIRCUITPY_AUDIOMIXER = 1
 endif