diff --git a/test/run_filter.cxx b/test/run_filter.cxx
index b148028cf..dd85b6fd0 100644
--- a/test/run_filter.cxx
+++ b/test/run_filter.cxx
@@ -27,6 +27,7 @@
 #include "pcm/Volume.hxx"
 #include "mixer/MixerControl.hxx"
 #include "system/Error.hxx"
+#include "system/FileDescriptor.hxx"
 #include "util/ConstBuffer.hxx"
 #include "util/StringBuffer.hxx"
 #include "util/RuntimeError.hxx"
@@ -39,8 +40,6 @@
 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>
-#include <errno.h>
-#include <unistd.h>
 
 void
 mixer_set_volume(gcc_unused Mixer *mixer,
@@ -61,9 +60,9 @@ LoadFilter(const ConfigData &config, const char *name)
 }
 
 static size_t
-ReadOrThrow(int fd, void *buffer, size_t size)
+ReadOrThrow(FileDescriptor fd, void *buffer, size_t size)
 {
-	auto nbytes = read(fd, buffer, size);
+	auto nbytes = fd.Read(buffer, size);
 	if (nbytes < 0)
 		throw MakeErrno("Read failed");
 
@@ -71,7 +70,7 @@ ReadOrThrow(int fd, void *buffer, size_t size)
 }
 
 static void
-FullRead(int fd, void *_buffer, size_t size)
+FullRead(FileDescriptor fd, void *_buffer, size_t size)
 {
 	auto buffer = (uint8_t *)_buffer;
 
@@ -86,7 +85,7 @@ FullRead(int fd, void *_buffer, size_t size)
 }
 
 static size_t
-ReadFrames(int fd, void *_buffer, size_t size, size_t frame_size)
+ReadFrames(FileDescriptor fd, void *_buffer, size_t size, size_t frame_size)
 {
 	auto buffer = (uint8_t *)_buffer;
 
@@ -141,17 +140,20 @@ try {
 
 	/* play */
 
+	FileDescriptor input_fd(STDIN_FILENO);
+	FileDescriptor output_fd(STDOUT_FILENO);
+
 	while (true) {
 		char buffer[4096];
 
-		ssize_t nbytes = ReadFrames(0, buffer, sizeof(buffer),
+		ssize_t nbytes = ReadFrames(input_fd, buffer, sizeof(buffer),
 					    in_frame_size);
 		if (nbytes == 0)
 			break;
 
 		auto dest = filter->FilterPCM({(const void *)buffer, (size_t)nbytes});
 
-		nbytes = write(1, dest.data, dest.size);
+		nbytes = output_fd.Write(dest.data, dest.size);
 		if (nbytes < 0) {
 			fprintf(stderr, "Failed to write: %s\n",
 				strerror(errno));