diff --git a/src/decoder/plugins/MadDecoderPlugin.cxx b/src/decoder/plugins/MadDecoderPlugin.cxx
index 4ad0efc0d..b422178d2 100644
--- a/src/decoder/plugins/MadDecoderPlugin.cxx
+++ b/src/decoder/plugins/MadDecoderPlugin.cxx
@@ -23,6 +23,7 @@
 #include "input/InputStream.hxx"
 #include "config/Block.hxx"
 #include "tag/Id3Scan.hxx"
+#include "tag/Id3ReplayGain.hxx"
 #include "tag/Rva2.hxx"
 #include "tag/Handler.hxx"
 #include "tag/ReplayGain.hxx"
@@ -254,40 +255,6 @@ MadDecoder::FillBuffer()
 	return true;
 }
 
-#ifdef ENABLE_ID3TAG
-static bool
-parse_id3_replay_gain_info(ReplayGainInfo &rgi,
-			   struct id3_tag *tag)
-{
-	bool found = false;
-
-	rgi.Clear();
-
-	struct id3_frame *frame;
-	for (unsigned i = 0; (frame = id3_tag_findframe(tag, "TXXX", i)); i++) {
-		if (frame->nfields < 3)
-			continue;
-
-		char *const key = (char *)
-		    id3_ucs4_latin1duplicate(id3_field_getstring
-					     (&frame->fields[1]));
-		char *const value = (char *)
-		    id3_ucs4_latin1duplicate(id3_field_getstring
-					     (&frame->fields[2]));
-
-		if (ParseReplayGainTag(rgi, key, value))
-			found = true;
-
-		free(key);
-		free(value);
-	}
-
-	return found ||
-		/* fall back on RVA2 if no replaygain tags found */
-		tag_rva2_parse(tag, rgi);
-}
-#endif
-
 #ifdef ENABLE_ID3TAG
 gcc_pure
 static MixRampInfo
@@ -358,7 +325,7 @@ MadDecoder::ParseId3(size_t tagsize, Tag **mpd_tag)
 	if (client != nullptr) {
 		ReplayGainInfo rgi;
 
-		if (parse_id3_replay_gain_info(rgi, id3_tag)) {
+		if (Id3ToReplayGainInfo(rgi, id3_tag)) {
 			client->SubmitReplayGain(&rgi);
 			found_replay_gain = true;
 		}
diff --git a/src/tag/Id3ReplayGain.cxx b/src/tag/Id3ReplayGain.cxx
new file mode 100644
index 000000000..94a5a0bc4
--- /dev/null
+++ b/src/tag/Id3ReplayGain.cxx
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2003-2018 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "config.h"
+#include "Id3ReplayGain.hxx"
+#include "Rva2.hxx"
+#include "ReplayGain.hxx"
+#include "ReplayGainInfo.hxx"
+
+#include <id3tag.h>
+
+#include <stdlib.h>
+
+bool
+Id3ToReplayGainInfo(ReplayGainInfo &rgi, const struct id3_tag *tag) noexcept
+{
+	bool found = false;
+
+	rgi.Clear();
+
+	struct id3_frame *frame;
+	for (unsigned i = 0; (frame = id3_tag_findframe(tag, "TXXX", i)); i++) {
+		if (frame->nfields < 3)
+			continue;
+
+		char *const key = (char *)
+		    id3_ucs4_latin1duplicate(id3_field_getstring
+					     (&frame->fields[1]));
+		char *const value = (char *)
+		    id3_ucs4_latin1duplicate(id3_field_getstring
+					     (&frame->fields[2]));
+
+		if (ParseReplayGainTag(rgi, key, value))
+			found = true;
+
+		free(key);
+		free(value);
+	}
+
+	return found ||
+		/* fall back on RVA2 if no replaygain tags found */
+		tag_rva2_parse(tag, rgi);
+}
diff --git a/src/tag/Id3ReplayGain.hxx b/src/tag/Id3ReplayGain.hxx
new file mode 100644
index 000000000..642b7ce7b
--- /dev/null
+++ b/src/tag/Id3ReplayGain.hxx
@@ -0,0 +1,31 @@
+/*
+ * Copyright 2003-2018 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_TAG_ID3_REPLAY_GAIN_HXX
+#define MPD_TAG_ID3_REPLAY_GAIN_HXX
+
+#include "check.h"
+
+struct id3_tag;
+struct ReplayGainInfo;
+
+bool
+Id3ToReplayGainInfo(ReplayGainInfo &rgi, const struct id3_tag *tag) noexcept;
+
+#endif
diff --git a/src/tag/meson.build b/src/tag/meson.build
index 8e23c879c..b0121a71d 100644
--- a/src/tag/meson.build
+++ b/src/tag/meson.build
@@ -27,6 +27,7 @@ if libid3tag_dep.found()
   tag_sources += [
     'Id3Load.cxx',
     'Id3Scan.cxx',
+    'Id3ReplayGain.cxx',
     'Rva2.cxx',
     'Riff.cxx',
     'Aiff.cxx',