diff --git a/docs/LightningModule/RequiredTrainerInterface.md b/docs/LightningModule/RequiredTrainerInterface.md
index 34a077f924..e5a0722efc 100644
--- a/docs/LightningModule/RequiredTrainerInterface.md
+++ b/docs/LightningModule/RequiredTrainerInterface.md
@@ -52,7 +52,7 @@ class CoolModel(pl.LightningModule):
         y_hat = self.forward(x)
         return {'loss': F.cross_entropy(y_hat, y)(y_hat, y)}
 
-    def validation_step(self, batch, batch_nb):
+    def validation_step(self, batch, batch_nb, dataloader_i):
         # OPTIONAL
         x, y = batch
         y_hat = self.forward(x)