diff --git a/pddl/logic/predicates.py b/pddl/logic/predicates.py
index 2760135..c039ada 100644
--- a/pddl/logic/predicates.py
+++ b/pddl/logic/predicates.py
@@ -171,6 +171,14 @@ def __repr__(self) -> str:
         """Get the string representation."""
         return f"{type(self).__name__}({self.predicate}, {self.condition})"
 
+    def __eq__(self, other):
+        """Override equal operator."""
+        return (
+            isinstance(other, DerivedPredicate)
+            and self.predicate == other.predicate
+            and self.condition == other.condition
+        )
+
     def __lt__(self, other):
         """Compare with another object."""
         if isinstance(other, DerivedPredicate):