diff --git a/biscuit-auth/src/error.rs b/biscuit-auth/src/error.rs
index eda089bf..295b2228 100644
--- a/biscuit-auth/src/error.rs
+++ b/biscuit-auth/src/error.rs
@@ -171,7 +171,7 @@ pub enum Signature {
 #[derive(Error, Clone, Debug, PartialEq, Eq)]
 #[cfg_attr(feature = "serde-error", derive(serde::Serialize, serde::Deserialize))]
 pub enum Logic {
-    #[error("a rule provided by a block is generating facts with the authority or ambient tag, or has head variables not used in its body")]
+    #[error("a rule provided by a block is producing a fact with unbound variables")]
     InvalidBlockRule(u32, String),
     #[error("{policy}, and the following checks failed: {checks:?}")]
     Unauthorized {