diff --git a/fluidsynth.py b/fluidsynth.py
index 47d3328..19c5eee 100644
--- a/fluidsynth.py
+++ b/fluidsynth.py
@@ -1100,4 +1100,4 @@ def raw_audio_string(data):
 
     """
     import numpy
-    return (data.astype(numpy.int16)).tostring()
+    return (data.astype(numpy.int16)).tobytes()