diff --git a/libraries/mbed/targets/hal/TARGET_WIZNET/TARGET_W7500x/analogin_api.c b/libraries/mbed/targets/hal/TARGET_WIZNET/TARGET_W7500x/analogin_api.c
index af28f7924e..1a2c52af9f 100644
--- a/libraries/mbed/targets/hal/TARGET_WIZNET/TARGET_W7500x/analogin_api.c
+++ b/libraries/mbed/targets/hal/TARGET_WIZNET/TARGET_W7500x/analogin_api.c
@@ -27,7 +27,7 @@
 
 ADC_TypeDef * AdcHandle;
 
-int adc_inited = 0;
+static int adc_inited = 0;
 
 void analogin_init(analogin_t *obj, PinName pin)
 {