--- a/src/decoder/plugins/FluidsynthDecoderPlugin.cxx
+++ b/src/decoder/plugins/FluidsynthDecoderPlugin.cxx
@@ -64,7 +64,11 @@ fluidsynth_level_to_mpd(enum fluid_log_l
  * logging library.
  */
 static void
+#if FLUIDSYNTH_VERSION_MAJOR == 1
 fluidsynth_mpd_log_function(int level, char *message, gcc_unused void *data)
+#else
+fluidsynth_mpd_log_function(int level, const char *message, gcc_unused void *data)
+#endif
 {
 	Log(fluidsynth_domain,
 	    fluidsynth_level_to_mpd(fluid_log_level(level)),