diff --git a/NEWS b/NEWS
index 06a665c97..ba229d81c 100644
--- a/NEWS
+++ b/NEWS
@@ -51,6 +51,9 @@ New in spot 2.4.0.dev (not yet released)
     recognize more if the original language can not be expressed with
     a co-Büchi acceptance condition.
 
+  - The function spot::is_recurrence() is now public. It checks if a formula
+    has the reccurence property.
+
   Deprecation notices:
 
   (These functions still work but compilers emit warnings.)
diff --git a/spot/tl/hierarchy.cc b/spot/tl/hierarchy.cc
index 4ed8e4506..a73ce59ff 100644
--- a/spot/tl/hierarchy.cc
+++ b/spot/tl/hierarchy.cc
@@ -30,31 +30,30 @@
 
 namespace spot
 {
-  namespace
+  bool
+  is_recurrence(formula f, const twa_graph_ptr& aut)
   {
-    static bool is_recurrence(formula f, const twa_graph_ptr& aut)
-    {
-      if (f.is_syntactic_recurrence() || is_universal(aut))
+    if (f.is_syntactic_recurrence() || is_universal(aut))
+      return true;
+    // If aut is a non-deterministic TGBA, we do
+    // TGBA->DPA->DRA->(D?)BA.  The conversion from DRA to
+    // BA will preserve determinism if possible.
+    spot::postprocessor p;
+    p.set_type(spot::postprocessor::Generic);
+    p.set_pref(spot::postprocessor::Deterministic
+               | spot::postprocessor::SBAcc);
+    p.set_level(spot::postprocessor::Low);
+    auto dra = p.run(aut);
+    if (dra->acc().is_generalized_buchi())
+      {
         return true;
-      // If aut is a non-deterministic TGBA, we do
-      // TGBA->DPA->DRA->(D?)BA.  The conversion from DRA to
-      // BA will preserve determinism if possible.
-      spot::postprocessor p;
-      p.set_type(spot::postprocessor::Generic);
-      p.set_pref(spot::postprocessor::Deterministic);
-      p.set_level(spot::postprocessor::Low);
-      auto dra = p.run(aut);
-      if (dra->acc().is_generalized_buchi())
-        {
-          return true;
-        }
-      else
-        {
-          auto ba = rabin_to_buchi_maybe(to_generalized_rabin(dra));
-          assert(ba);
-          return is_deterministic(ba);
-        }
-    }
+      }
+    else
+      {
+        auto ba = rabin_to_buchi_maybe(to_generalized_rabin(dra));
+        assert(ba);
+        return is_deterministic(ba);
+      }
   }
 
   char mp_class(formula f)
diff --git a/spot/tl/hierarchy.hh b/spot/tl/hierarchy.hh
index 88def1831..ea9b4b672 100644
--- a/spot/tl/hierarchy.hh
+++ b/spot/tl/hierarchy.hh
@@ -20,9 +20,14 @@
 #pragma once
 
 #include <spot/tl/formula.hh>
+#include <spot/twa/fwd.hh>
 
 namespace spot
 {
+  /// \brief Return true if the formula has the recurrence property.
+  SPOT_API
+  bool is_recurrence(formula f, const twa_graph_ptr& aut);
+
   /// \brief Return the class of \a f in the temporal hierarchy of Manna
   /// and Pnueli (PODC'90).
   ///