diff --git a/ports/espressif/mpconfigport.mk b/ports/espressif/mpconfigport.mk
index 1b9808ad6494..63cea3d0a8f3 100644
--- a/ports/espressif/mpconfigport.mk
+++ b/ports/espressif/mpconfigport.mk
@@ -38,6 +38,7 @@ CIRCUITPY_NVM ?= 1
 CIRCUITPY_PS2IO ?= 1
 CIRCUITPY_RGBMATRIX ?= 1
 CIRCUITPY_ROTARYIO ?= 1
+CIRCUITPY_SYNTHIO_MAX_CHANNELS ?= 12
 CIRCUITPY_TOUCHIO_USE_NATIVE ?= 1
 CIRCUITPY_WATCHDOG ?= 1
 CIRCUITPY_WIFI ?= 1