diff --git a/Makefile.am b/Makefile.am
index b2c0161cb..0e26cafea 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1328,6 +1328,7 @@ OUTPUT_LIBS = \
 
 OUTPUT_API_SRC = \
 	src/output/OutputAPI.hxx \
+	src/output/Internal.cxx \
 	src/output/Internal.hxx \
 	src/output/Wrapper.hxx \
 	src/output/Registry.cxx src/output/Registry.hxx \
diff --git a/src/output/Internal.cxx b/src/output/Internal.cxx
new file mode 100644
index 000000000..07bb5b128
--- /dev/null
+++ b/src/output/Internal.cxx
@@ -0,0 +1,45 @@
+/*
+ * Copyright 2003-2016 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 "Internal.hxx"
+#include "MusicPipe.hxx"
+#include "MusicChunk.hxx"
+
+#include <assert.h>
+
+bool
+AudioOutput::IsChunkConsumed(const MusicChunk &chunk) const
+{
+	if (!open)
+		return true;
+
+	if (current_chunk == nullptr)
+		return false;
+
+	assert(&chunk == current_chunk ||
+	       pipe->Contains(current_chunk));
+
+	if (&chunk != current_chunk) {
+		assert(chunk.next != nullptr);
+		return true;
+	}
+
+	return current_chunk_finished && chunk.next == nullptr;
+}
diff --git a/src/output/Internal.hxx b/src/output/Internal.hxx
index 9426886c9..0832a7012 100644
--- a/src/output/Internal.hxx
+++ b/src/output/Internal.hxx
@@ -394,6 +394,20 @@ public:
 	 */
 	void LockAllowPlay();
 
+	/**
+	 * Did we already consumed this chunk?
+	 *
+	 * Caller must lock the mutex.
+	 */
+	gcc_pure
+	bool IsChunkConsumed(const MusicChunk &chunk) const;
+
+	gcc_pure
+	bool LockIsChunkConsumed(const MusicChunk &chunk) {
+		const ScopeLock protect(mutex);
+		return IsChunkConsumed(chunk);
+	}
+
 private:
 	void CommandFinished();
 
diff --git a/src/output/MultipleOutputs.cxx b/src/output/MultipleOutputs.cxx
index 9758eb87e..2da317eff 100644
--- a/src/output/MultipleOutputs.cxx
+++ b/src/output/MultipleOutputs.cxx
@@ -251,40 +251,12 @@ MultipleOutputs::Open(const AudioFormat audio_format,
 	}
 }
 
-/**
- * Has the specified audio output already consumed this chunk?
- */
-gcc_pure
-static bool
-chunk_is_consumed_in(const AudioOutput *ao,
-		     gcc_unused const MusicPipe *pipe,
-		     const MusicChunk *chunk)
-{
-	if (!ao->open)
-		return true;
-
-	if (ao->current_chunk == nullptr)
-		return false;
-
-	assert(chunk == ao->current_chunk ||
-	       pipe->Contains(ao->current_chunk));
-
-	if (chunk != ao->current_chunk) {
-		assert(chunk->next != nullptr);
-		return true;
-	}
-
-	return ao->current_chunk_finished && chunk->next == nullptr;
-}
-
 bool
 MultipleOutputs::IsChunkConsumed(const MusicChunk *chunk) const
 {
-	for (auto ao : outputs) {
-		const ScopeLock protect(ao->mutex);
-		if (!chunk_is_consumed_in(ao, pipe, chunk))
+	for (auto ao : outputs)
+		if (!ao->LockIsChunkConsumed(*chunk))
 			return false;
-	}
 
 	return true;
 }