diff --git a/src/mainboard/google/rex/variants/rex0/overridetree.cb b/src/mainboard/google/rex/variants/rex0/overridetree.cb
index 730af8bb30..e0cbc6e7d3 100644
--- a/src/mainboard/google/rex/variants/rex0/overridetree.cb
+++ b/src/mainboard/google/rex/variants/rex0/overridetree.cb
@@ -1,5 +1,11 @@
 chip soc/intel/meteorlake
 
+	register "serial_io_gspi_mode" = "{
+		[PchSerialIoIndexGSPI0] = PchSerialIoDisabled,
+		[PchSerialIoIndexGSPI1] = PchSerialIoPci,
+		[PchSerialIoIndexGSPI2] = PchSerialIoDisabled,
+	}"
+
 	register "serial_io_i2c_mode" = "{
 		[PchSerialIoIndexI2C0] = PchSerialIoPci,
 		[PchSerialIoIndexI2C1] = PchSerialIoPci,