diff --git a/src/entity/relation.rs b/src/entity/relation.rs
index 9e3c565e..95deeb58 100644
--- a/src/entity/relation.rs
+++ b/src/entity/relation.rs
@@ -168,6 +168,8 @@ impl RelationDef {
     /// This method takes a closure with two parameters
     /// denoting the left-hand side and right-hand side table in the join expression.
     ///
+    /// This replaces the current condition if it is already set.
+    ///
     /// # Examples
     ///
     /// ```