diff --git a/src/guitarpro/gp3.py b/src/guitarpro/gp3.py
index d14d936..23e49f7 100644
--- a/src/guitarpro/gp3.py
+++ b/src/guitarpro/gp3.py
@@ -1281,8 +1281,9 @@ def writeChord(self, chord):
     def writeOldChord(self, chord):
         self.writeIntByteSizeString(chord.name)
         self.writeI32(chord.firstFret)
-        for fret in clamp(chord.strings, 6, fillvalue=-1):
-            self.writeI32(fret)
+        if chord.firstFret:
+            for fret in clamp(chord.strings, 6, fillvalue=-1):
+                self.writeI32(fret)
 
     def writeNewChord(self, chord):
         self.writeBool(chord.sharp)
diff --git a/tests/Chord Old Format.gp3 b/tests/Chord Old Format.gp3
new file mode 100644
index 0000000..588f46b
Binary files /dev/null and b/tests/Chord Old Format.gp3 differ
diff --git a/tests/test_conversion.py b/tests/test_conversion.py
index 28c1bc5..19b4649 100644
--- a/tests/test_conversion.py
+++ b/tests/test_conversion.py
@@ -10,6 +10,7 @@
 TESTS = [
     'Effects.gp3',
     'Chords.gp3',
+    'Chord Old Format.gp3',
     'Duration.gp3',
     'Harmonics.gp3',
     'Measure Header.gp3',