diff --git a/action.yml b/action.yml
index 23c6000..36b5f26 100644
--- a/action.yml
+++ b/action.yml
@@ -8,7 +8,8 @@ branding:
 inputs:
   toolchain:
     description: Rust toolchain specification -- see https://rust-lang.github.io/rustup/concepts/toolchains.html#toolchain-specification
-    required: true
+    required: false
+    default: nightly
   targets:
     description: Comma-separated list of target triples to install for this toolchain
     required: false