diff --git a/src/decoder/Client.hxx b/src/decoder/Client.hxx
index 15710a3ca..d77f2ed8e 100644
--- a/src/decoder/Client.hxx
+++ b/src/decoder/Client.hxx
@@ -23,6 +23,7 @@
 #include "check.h"
 #include "DecoderCommand.hxx"
 #include "Chrono.hxx"
+#include "input/Ptr.hxx"
 #include "Compiler.h"
 
 #include <stdint.h>
@@ -31,7 +32,6 @@ struct AudioFormat;
 struct Tag;
 struct ReplayGainInfo;
 class MixRampInfo;
-class InputStream;
 
 /**
  * An interface between the decoder plugin and the MPD core.
@@ -89,6 +89,15 @@ public:
 	 */
 	virtual void SeekError() = 0;
 
+	/**
+	 * Open a new #InputStream and wait until it's ready.
+	 *
+	 * Throws #StopDecoder if DecoderCommand::STOP was received.
+	 *
+	 * Throws std::runtime_error on error.
+	 */
+	virtual InputStreamPtr OpenUri(const char *uri) = 0;
+
 	/**
 	 * Sets the time stamp for the next data chunk [seconds].  The MPD
 	 * core automatically counts it up, and a decoder plugin only needs to
diff --git a/src/decoder/DecoderAPI.cxx b/src/decoder/DecoderAPI.cxx
index 362df4e03..7db621142 100644
--- a/src/decoder/DecoderAPI.cxx
+++ b/src/decoder/DecoderAPI.cxx
@@ -251,14 +251,11 @@ Decoder::SeekError()
 }
 
 InputStreamPtr
-decoder_open_uri(DecoderClient &client, const char *uri)
+Decoder::OpenUri(const char *uri)
 {
-	auto &decoder = (Decoder &)client;
+	assert(dc.state == DecoderState::START ||
+	       dc.state == DecoderState::DECODE);
 
-	assert(decoder.dc.state == DecoderState::START ||
-	       decoder.dc.state == DecoderState::DECODE);
-
-	DecoderControl &dc = decoder.dc;
 	Mutex &mutex = dc.mutex;
 	Cond &cond = dc.cond;
 
diff --git a/src/decoder/DecoderAPI.hxx b/src/decoder/DecoderAPI.hxx
index f2d010c16..91aea81e3 100644
--- a/src/decoder/DecoderAPI.hxx
+++ b/src/decoder/DecoderAPI.hxx
@@ -54,16 +54,6 @@ class DecoderClient;
  */
 class StopDecoder {};
 
-/**
- * Open a new #InputStream and wait until it's ready.
- *
- * Throws #StopDecoder if DecoderCommand::STOP was received.
- *
- * Throws std::runtime_error on error.
- */
-InputStreamPtr
-decoder_open_uri(DecoderClient &decoder, const char *uri);
-
 /**
  * Blocking read from the input stream.
  *
diff --git a/src/decoder/DecoderInternal.hxx b/src/decoder/DecoderInternal.hxx
index 61576bd32..9155da501 100644
--- a/src/decoder/DecoderInternal.hxx
+++ b/src/decoder/DecoderInternal.hxx
@@ -124,6 +124,7 @@ struct Decoder final : DecoderClient {
 	SongTime GetSeekTime() override;
 	uint64_t GetSeekFrame() override;
 	void SeekError() override;
+	InputStreamPtr OpenUri(const char *uri) override;
 	void SubmitTimestamp(double t) override;
 	DecoderCommand SubmitData(InputStream *is,
 				  const void *data, size_t length,
diff --git a/src/decoder/plugins/WavpackDecoderPlugin.cxx b/src/decoder/plugins/WavpackDecoderPlugin.cxx
index 685c1b66d..fb4ed7a16 100644
--- a/src/decoder/plugins/WavpackDecoderPlugin.cxx
+++ b/src/decoder/plugins/WavpackDecoderPlugin.cxx
@@ -496,7 +496,7 @@ wavpack_open_wvc(DecoderClient &client, const char *uri)
 	};
 
 	try {
-		return decoder_open_uri(client, uri);
+		return client.OpenUri(uri);
 	} catch (const std::runtime_error &) {
 		return nullptr;
 	}
diff --git a/test/FakeDecoderAPI.cxx b/test/FakeDecoderAPI.cxx
index 3c4539af1..cd8d52cf2 100644
--- a/test/FakeDecoderAPI.cxx
+++ b/test/FakeDecoderAPI.cxx
@@ -74,10 +74,9 @@ FakeDecoder::SeekError()
 }
 
 InputStreamPtr
-decoder_open_uri(DecoderClient &client, const char *uri)
+FakeDecoder::OpenUri(const char *uri)
 {
-	auto &decoder = (FakeDecoder &)client;
-	return InputStream::OpenReady(uri, decoder.mutex, decoder.cond);
+	return InputStream::OpenReady(uri, mutex, cond);
 }
 
 size_t
diff --git a/test/FakeDecoderAPI.hxx b/test/FakeDecoderAPI.hxx
index d21d1615d..5b9256a74 100644
--- a/test/FakeDecoderAPI.hxx
+++ b/test/FakeDecoderAPI.hxx
@@ -39,6 +39,7 @@ struct FakeDecoder final : DecoderClient {
 	SongTime GetSeekTime() override;
 	uint64_t GetSeekFrame() override;
 	void SeekError() override;
+	InputStreamPtr OpenUri(const char *uri) override;
 	void SubmitTimestamp(double t) override;
 	DecoderCommand SubmitData(InputStream *is,
 				  const void *data, size_t length,