diff --git a/keras/layers/convolutional.py b/keras/layers/convolutional.py
index 542bb82c9..32de89bc1 100644
--- a/keras/layers/convolutional.py
+++ b/keras/layers/convolutional.py
@@ -256,6 +256,9 @@ class Conv1D(_Conv):
             Specifying any stride value != 1 is incompatible with specifying
             any `dilation_rate` value != 1.
         padding: One of `"valid"`, `"causal"` or `"same"` (case-insensitive).
+            `"valid"` means "no padding".
+            `"same"` results in padding the input such that
+            the output has the same length as the original input.
             `"causal"` results in causal (dilated) convolutions, e.g. output[t]
             does not depend on input[t+1:]. Useful when modeling temporal data
             where the model should not violate the temporal order.