diff --git a/NEWS b/NEWS
index feb630320..220947d3a 100644
--- a/NEWS
+++ b/NEWS
@@ -35,6 +35,9 @@ New in spot 2.11.5.dev  (not yet released)
     where thousands of different filenames can be created failed with
     "Too many open files".  (Issue #534)
 
+  - Using --format=... on a tool that output formulas would force
+    the output on standard output, even when --output was given.
+
 
 New in spot 2.11.5  (2023-04-20)
 
diff --git a/bin/common_output.cc b/bin/common_output.cc
index 2f851f109..16beca34d 100644
--- a/bin/common_output.cc
+++ b/bin/common_output.cc
@@ -225,7 +225,7 @@ namespace
     }
   };
 
-  class formula_printer final: protected spot::formater
+  class formula_printer final: public spot::formater
   {
   public:
     formula_printer(std::ostream& os, const char* format)
@@ -399,6 +399,7 @@ output_formula(std::ostream& out,
     {
       formula_with_location fl = { f, filename, linenum,
                                    index, prefix, suffix };
+      format->set_output(out);
       format->print(fl, ptimer);
     }
 }
diff --git a/tests/core/serial.test b/tests/core/serial.test
index 6f4c48c6a..7914316c8 100755
--- a/tests/core/serial.test
+++ b/tests/core/serial.test
@@ -78,3 +78,16 @@ test 2000 = `ls -l randaut-*.hoa | wc -l`
 # likewise for LTL formulas
 randltl 2 -n 2000 -o randltl-%l.ltl
 test 2000 = `ls -l randltl-*.ltl | wc -l`
+
+
+# Test the code path that works that has to reopen files
+randltl -n100 --tree-size 1 26 --allow-dups -o '%f'.ltl --format=pass1
+randltl -n100 --tree-size 1 26 --allow-dups -o '>>%f'.ltl --format=pass2
+(uniq -c p1.ltl; uniq -c p20.ltl) | sed 's/^ *\([0-9][0-9]*\)  */\1 /g' >out
+cat >expected <<EOF
+4 pass1
+4 pass2
+5 pass1
+5 pass2
+EOF
+diff out expected