diff --git a/firmware/common/wm8731.cpp b/firmware/common/wm8731.cpp
index 68086d66..2965ad26 100644
--- a/firmware/common/wm8731.cpp
+++ b/firmware/common/wm8731.cpp
@@ -25,6 +25,18 @@
 namespace wolfson {
 namespace wm8731 {
 
+void WM8731::configure_interface_i2s_slave() {
+	write(DigitalAudioInterfaceFormat {
+		.format = 2,
+		.iwl = 0,
+		.lrp = 0,
+		.lrswap = 0,
+		.ms = 0,
+		.bclkinv = 0,
+		.reserved0 = 0,
+	});
+}
+
 void WM8731::init() {
 	reset();
 
@@ -49,15 +61,7 @@ void WM8731::init() {
 	// 	.reserved0 = 0,
 	// });
 
-	write(DigitalAudioInterfaceFormat {
-		.format = 2,
-		.iwl = 0,
-		.lrp = 0,
-		.lrswap = 0,
-		.ms = 0,
-		.bclkinv = 0,
-		.reserved0 = 0,
-	});
+	configure_interface_i2s_slave();
 
 	write(DigitalAudioPathControl {
 		.adchpd = 0,
diff --git a/firmware/common/wm8731.hpp b/firmware/common/wm8731.hpp
index b2c52778..f4128658 100644
--- a/firmware/common/wm8731.hpp
+++ b/firmware/common/wm8731.hpp
@@ -375,6 +375,8 @@ private:
 	RegisterMap map { default_after_reset };
 	volume_t headphone_volume = -60.0_dB;
 
+	void configure_interface_i2s_slave();
+
 	bool write(const Register reg);
 	
 	bool write(const address_t reg_address, const reg_t value);