diff --git a/spot/twaalgos/forq_contains.cc b/spot/twaalgos/forq_contains.cc
index adf7c597a..ccb635839 100644
--- a/spot/twaalgos/forq_contains.cc
+++ b/spot/twaalgos/forq_contains.cc
@@ -630,7 +630,7 @@ namespace spot
                                "acceptance conditions.");
     if (lhs->get_dict() != rhs->get_dict())
       throw std::runtime_error
-        ("The two input graphs must utilize the same twa_dict.");
+        ("The two input automata must use the same twa_dict.");
     if (lhs->ap() != rhs->ap())
       throw std::runtime_error("The two input graphs must use the same set "
                                "of APs");
@@ -648,7 +648,7 @@ namespace spot
 
   bool contains_forq(forq::const_graph lhs, forq::const_graph rhs)
   {
-    return !difference_word_forq(lhs, rhs);
+    return !difference_word_forq(rhs, lhs);
   }
 }
 
diff --git a/spot/twaalgos/forq_contains.hh b/spot/twaalgos/forq_contains.hh
index 3d49c5498..9e7c792af 100644
--- a/spot/twaalgos/forq_contains.hh
+++ b/spot/twaalgos/forq_contains.hh
@@ -41,10 +41,10 @@ namespace spot
 
   /// \ingroup containment
   /// \brief Returns a boolean value indicating
-  /// whether \a left is included in the language of \a right.
+  /// whether the language of \a left includes in the language of \a right.
   ///
   /// This implements a FORQ-based language containment algorithm
-  /// to check whether L(left)⊆L(right). \cite doveri.22.cav
+  /// to check whether L(left)⊇L(right). \cite doveri.22.cav
   ///
   /// \pre Automata \a left and \a right should be non-alternating
   /// Büchi-automata.
diff --git a/tests/python/forq_contains.py b/tests/python/forq_contains.py
index be510e66c..3e47bec87 100644
--- a/tests/python/forq_contains.py
+++ b/tests/python/forq_contains.py
@@ -23,7 +23,7 @@ from unittest import TestCase
 tc = TestCase()
 
 def do_test(subset, superset, expected=True):
-    result = spot.contains_forq(subset, superset)
+    result = spot.contains_forq(superset, subset)
     truth = spot.contains(superset, subset)
     tc.assertTrue(truth == expected)
     tc.assertTrue(result == truth)
@@ -324,4 +324,3 @@ State: 11 {0}
 --END--""")
 
 do_symmetric_test(subset, superset)
-