diff --git a/core/libs/prx/libSceVoice/Export.cpp b/core/libs/prx/libSceVoice/Export.cpp
index 898511c88..ba55f55dd 100644
--- a/core/libs/prx/libSceVoice/Export.cpp
+++ b/core/libs/prx/libSceVoice/Export.cpp
@@ -24,6 +24,7 @@ struct Port {
     std::int32_t type;
     float volume;
     std::uint32_t bitrate;
+    bool muted = false;
 };
 
 struct Voice {
@@ -204,8 +205,18 @@ int APS5_VABI sceVoiceWriteToIPort(uint32_t input_port_id, const void* data, uin
     return 0;
 }
 
-int APS5_VABI sceVoiceSetMuteFlag() {
-    NotImplemented_nid_no_patch(__func__);
+int APS5_VABI sceVoiceSetMuteFlag(uint32_t port_id, bool muted) {
+    auto& voice = State();
+    std::lock_guard lock(voice.mutex);
+    RequirePort(voice, port_id, __func__).muted = muted;
+    return 0;
+}
+
+int APS5_VABI sceVoiceGetMuteFlag(uint32_t port_id, bool* muted) {
+    if (muted == nullptr) APS5_INVALID_ARG_EX;
+    auto& voice = State();
+    std::lock_guard lock(voice.mutex);
+    *muted = RequirePort(voice, port_id, __func__).muted;
     return 0;
 }
 
diff --git a/docs/dev/TechnicalDebt.md b/docs/dev/TechnicalDebt.md
index 4656d0fbb..2bc086001 100644
--- a/docs/dev/TechnicalDebt.md
+++ b/docs/dev/TechnicalDebt.md
@@ -234,7 +234,6 @@ Throughout the project, every function at every stage either **does exactly what
 - [sceNgs2VoiceGetPortInfo](../../core/libs/prx/libSceNgs2.native/src/Voice.cpp) (libSceNgs2.native) - layout from shadPS4; the delay and destination input are zero because ports have neither yet
 - [sceNgs2ParseWaveformFile](../../core/libs/prx/libSceNgs2.native/src/Atrac9.cpp) (libSceNgs2.native) - the signature `(path, offset, info)` is taken from the call site of PPSA21402, which sets only three argument registers; the file is read from `offset` to its end, the data and block offsets are taken to be relative to the start of the file, not of `offset`, and an unreadable file throws. The audio unit fields of a 16-bit PCM waveform are assumed to be one sample frame per unit and per frame; `INVALID_WAVEFORM_DATA` for a `data` chunk that runs past the buffer or ends inside a frame is assumed, and looped PCM and other PCM formats throw
 - [sceSaveDataInitialize3](../../core/libs/prx/libSceSaveData.native/Export.cpp) (libSceSaveData.native) - a repeated initialize succeeds: PPSA12544's executable and its Unity SaveData plugin both initialize, and the plugin fails on any error. Initializations are counted and `sceSaveDataTerminate` ends the session at the last one; how the console pairs them is unknown
-- [sceVoiceSetMuteFlag](../../core/libs/prx/libSceVoice/Export.cpp) (libSceVoice) - unknown signature
 - [sceTextToSpeech2GetSystemStatus](../../core/libs/prx/libSceTextToSpeech2/Export.cpp) (libSceTextToSpeech2) - unknown signature
 - [sceCoredumpAttachUserMemoryFile](../../core/libs/prx/libkernel/System/src/Coredump.cpp) (libkernel) - unknown signature
 - [sceCoredumpAttachMemoryRegion](../../core/libs/prx/libkernel/System/src/Coredump.cpp) (libkernel) - unknown signature