diff --git a/Makefile.am b/Makefile.am
index 167b61768..357416a03 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1257,7 +1257,7 @@ endif
 
 if ENABLE_ENCODER
 noinst_PROGRAMS += test/run_encoder
-test_run_encoder_SOURCES = test/run_encoder.c \
+test_run_encoder_SOURCES = test/run_encoder.cxx \
 	test/stdbin.h \
 	src/tokenizer.c src/utils.c src/string_util.c \
 	src/Tag.cxx src/TagNames.c src/TagPool.cxx \
@@ -1295,7 +1295,7 @@ test_test_vorbis_encoder_LDADD = $(MPD_LIBS) \
 	$(GLIB_LIBS)
 endif
 
-test_software_volume_SOURCES = test/software_volume.c \
+test_software_volume_SOURCES = test/software_volume.cxx \
 	test/stdbin.h \
 	src/audio_check.c \
 	src/audio_parser.c
@@ -1311,7 +1311,7 @@ test_run_normalize_SOURCES = test/run_normalize.c \
 test_run_normalize_LDADD = \
 	$(GLIB_LIBS)
 
-test_run_convert_SOURCES = test/run_convert.c \
+test_run_convert_SOURCES = test/run_convert.cxx \
 	src/dsd2pcm/dsd2pcm.c \
 	src/audio_format.c \
 	src/audio_check.c \
diff --git a/src/audio_parser.h b/src/audio_parser.h
index 49926999e..bbe868f61 100644
--- a/src/audio_parser.h
+++ b/src/audio_parser.h
@@ -31,6 +31,10 @@
 
 struct audio_format;
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * Parses a string in the form "SAMPLE_RATE:BITS:CHANNELS" into an
  * #audio_format.
@@ -46,4 +50,8 @@ bool
 audio_format_parse(struct audio_format *dest, const char *src,
 		   bool mask, GError **error_r);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
diff --git a/src/pcm_volume.h b/src/pcm_volume.h
index 4a4a4e45a..c161a72c7 100644
--- a/src/pcm_volume.h
+++ b/src/pcm_volume.h
@@ -65,6 +65,10 @@ pcm_volume_dither(void)
 	return (r & 511) - ((r >> 9) & 511);
 }
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /**
  * Adjust the volume of the specified PCM buffer.
  *
@@ -79,4 +83,8 @@ pcm_volume(void *buffer, size_t length,
 	   enum sample_format format,
 	   int volume);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
diff --git a/test/run_convert.c b/test/run_convert.cxx
similarity index 98%
rename from test/run_convert.c
rename to test/run_convert.cxx
index bdb3d2cf0..a71ebc2c4 100644
--- a/test/run_convert.c
+++ b/test/run_convert.cxx
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
diff --git a/test/run_encoder.c b/test/run_encoder.cxx
similarity index 98%
rename from test/run_encoder.c
rename to test/run_encoder.cxx
index db4d3af9b..6a1412969 100644
--- a/test/run_encoder.c
+++ b/test/run_encoder.cxx
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -51,7 +51,6 @@ int main(int argc, char **argv)
 	struct encoder *encoder;
 	struct config_param *param;
 	static char buffer[32768];
-	ssize_t nbytes;
 
 	/* parse command line */
 
@@ -110,6 +109,7 @@ int main(int argc, char **argv)
 
 	/* do it */
 
+	ssize_t nbytes;
 	while ((nbytes = read(0, buffer, sizeof(buffer))) > 0) {
 		ret = encoder_write(encoder, buffer, nbytes, &error);
 		if (!ret) {
diff --git a/test/software_volume.c b/test/software_volume.cxx
similarity index 92%
rename from test/software_volume.c
rename to test/software_volume.cxx
index 2357da672..180686650 100644
--- a/test/software_volume.c
+++ b/test/software_volume.cxx
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2003-2011 The Music Player Daemon Project
+ * Copyright (C) 2003-2013 The Music Player Daemon Project
  * http://www.musicpd.org
  *
  * This program is free software; you can redistribute it and/or modify
@@ -59,7 +59,8 @@ int main(int argc, char **argv)
 		audio_format_init(&audio_format, 48000, SAMPLE_FORMAT_S16, 2);
 
 	while ((nbytes = read(0, buffer, sizeof(buffer))) > 0) {
-		if (!pcm_volume(buffer, nbytes, audio_format.format,
+		if (!pcm_volume(buffer, nbytes,
+				sample_format(audio_format.format),
 				PCM_VOLUME_1 / 2)) {
 			g_printerr("pcm_volume() has failed\n");
 			return 2;