diff --git a/cores/oak/core_esp8266_i2s.c b/cores/oak/core_esp8266_i2s.c
index 6c983f5..628f7ef 100644
--- a/cores/oak/core_esp8266_i2s.c
+++ b/cores/oak/core_esp8266_i2s.c
@@ -219,7 +219,7 @@ void ICACHE_FLASH_ATTR i2s_begin(){
   
   pinMode(esp8266_gpioToPin[2], FUNCTION_1); //I2SO_WS (LRCK)
   pinMode(esp8266_gpioToPin[3], FUNCTION_1); //I2SO_DATA (SDIN)
-  pinMode(esp8266_gpioToPin[5], FUNCTION_1); //I2SO_BCK (SCLK)
+  pinMode(esp8266_gpioToPin[15], FUNCTION_1); //I2SO_BCK (SCLK)
   
   I2S_CLK_ENABLE();
   I2SIC = 0x3F;