diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
index ec140fc4a0f5..bd662aaf664a 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-intel.c
@@ -320,6 +320,7 @@ static int intel_crosststamp(ktime_t *device,
 		acr_value |= PTP_ACR_ATSEN3;
 		break;
 	default:
+		mutex_unlock(&priv->aux_ts_lock);
 		return -EINVAL;
 	}
 	writel(acr_value, ptpaddr + PTP_ACR);