diff --git a/README.md b/README.md
index 6564e7d58..fbc26beb9 100644
--- a/README.md
+++ b/README.md
@@ -41,7 +41,7 @@ If you don't need them, disabling the default features may reduce code size and
 portable-atomic = { version = "1", default-features = false }
 ```
 
-If your crate supports no-std environment and requires atomic CAS, enabling the `require-cas` feature will allow the `portable-atomic` to display helpful error messages to users on targets requiring additional action on the user side to provide atomic CAS.
+If your crate supports no-std environment and requires atomic CAS, enabling the `require-cas` feature will allow the `portable-atomic` to display a [helpful error message](https://github.com/taiki-e/portable-atomic/pull/100) to users on targets requiring additional action on the user side to provide atomic CAS.
 
 ```toml
 [dependencies]
diff --git a/src/lib.rs b/src/lib.rs
index 3a481bb57..0665ad225 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -35,7 +35,7 @@ If you don't need them, disabling the default features may reduce code size and
 portable-atomic = { version = "1", default-features = false }
 ```
 
-If your crate supports no-std environment and requires atomic CAS, enabling the `require-cas` feature will allow the `portable-atomic` to display helpful error messages to users on targets requiring additional action on the user side to provide atomic CAS.
+If your crate supports no-std environment and requires atomic CAS, enabling the `require-cas` feature will allow the `portable-atomic` to display a [helpful error message](https://github.com/taiki-e/portable-atomic/pull/100) to users on targets requiring additional action on the user side to provide atomic CAS.
 
 ```toml
 [dependencies]