diff --git a/recording-daemon/output.c b/recording-daemon/output.c
index 31d076907..71aa29f7b 100644
--- a/recording-daemon/output.c
+++ b/recording-daemon/output.c
@@ -318,9 +318,9 @@ output_t *output_new_ext(metafile_t *mf, const char *type, const char *kind, con
 }
 
 #if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(61, 0, 0)
-int output_avio_write(void *opaque, const uint8_t *buf, int buf_size) {
+static int output_avio_write(void *opaque, const uint8_t *buf, int buf_size) {
 #else
-int output_avio_write(void *opaque, uint8_t *buf, int buf_size) {
+static int output_avio_write(void *opaque, uint8_t *buf, int buf_size) {
 #endif
 	output_t *o = opaque;
 	ssize_t written = fwrite(buf, buf_size, 1, o->fp);
@@ -329,16 +329,16 @@ int output_avio_write(void *opaque, uint8_t *buf, int buf_size) {
 	return AVERROR(errno);
 }
 
-int64_t output_avio_seek(void *opaque, int64_t offset, int whence) {
+static int64_t output_avio_seek(void *opaque, int64_t offset, int whence) {
 	output_t *o = opaque;
 	fseek(o->fp, offset, whence);
 	return ftell(o->fp);
 }
 
 #if LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(61, 0, 0)
-int output_avio_mem_write(void *opaque, const uint8_t *buf, int buf_size) {
+static int output_avio_mem_write(void *opaque, const uint8_t *buf, int buf_size) {
 #else
-int output_avio_mem_write(void *opaque, uint8_t *buf, int buf_size) {
+static int output_avio_mem_write(void *opaque, uint8_t *buf, int buf_size) {
 #endif
 	output_t *o = opaque;
 	g_string_overwrite_len(o->membuf, o->mempos, (const char *) buf, buf_size);
@@ -346,7 +346,7 @@ int output_avio_mem_write(void *opaque, uint8_t *buf, int buf_size) {
 	return buf_size;
 }
 
-int64_t output_avio_mem_seek(void *opaque, int64_t offset, int whence) {
+static int64_t output_avio_mem_seek(void *opaque, int64_t offset, int whence) {
 	output_t *o = opaque;
 	if (whence == SEEK_SET)
 		o->mempos = offset;