diff --git a/src/cubeb_wasapi.cpp b/src/cubeb_wasapi.cpp
index 0bb77261..592dab65 100644
--- a/src/cubeb_wasapi.cpp
+++ b/src/cubeb_wasapi.cpp
@@ -437,6 +437,10 @@ struct cubeb_stream {
    * practice, we read from the input stream in the output callback, so
    * this is not used, but it is necessary to start getting input data. */
   HANDLE input_available_event = 0;
+  /* Signaled by stream_start/stream_stop when the active state changes,
+     so the render thread can promote/demote its MMCSS task accordingly
+     instead of remaining promoted while idle. */
+  HANDLE mmcss_event = 0;
   /* Each cubeb_stream has its own thread. */
   HANDLE thread = 0;
   /* The lock protects all members that are touched by the render thread or
@@ -1503,8 +1507,9 @@ static unsigned int __stdcall wasapi_stream_render_loop(LPVOID stream)
   } com;
 
   bool is_playing = true;
-  HANDLE wait_array[4] = {stm->shutdown_event, stm->reconfigure_event,
-                          stm->refill_event, stm->input_available_event};
+  HANDLE wait_array[5] = {stm->shutdown_event, stm->mmcss_event,
+                          stm->reconfigure_event, stm->refill_event,
+                          stm->input_available_event};
   HANDLE mmcss_handle = NULL;
   HRESULT hr = 0;
   DWORD mmcss_task_index = 0;
@@ -1517,15 +1522,6 @@ static unsigned int __stdcall wasapi_stream_render_loop(LPVOID stream)
     return 0;
   }
 
-  /* We could consider using "Pro Audio" here for WebAudio and
-     maybe WebRTC. */
-  mmcss_handle = AvSetMmThreadCharacteristicsA("Audio", &mmcss_task_index);
-  if (!mmcss_handle) {
-    /* This is not fatal, but we might glitch under heavy load. */
-    LOG("Unable to use mmcss to bump the render thread priority: %lx",
-        GetLastError());
-  }
-
   while (is_playing) {
     DWORD waitResult = WaitForMultipleObjects(ARRAY_LENGTH(wait_array),
                                               wait_array, FALSE, INFINITE);
@@ -1539,7 +1535,30 @@ static unsigned int __stdcall wasapi_stream_render_loop(LPVOID stream)
       }
       continue;
     }
-    case WAIT_OBJECT_0 + 1: { /* reconfigure */
+    case WAIT_OBJECT_0 + 1: { /* mmcss: active state changed */
+      /* stm->active was set by wasapi_stream_start/_stop before signaling,
+         and SetEvent provides the necessary memory barrier. */
+      if (stm->active && !mmcss_handle) {
+        /* We could consider using "Pro Audio" here for WebAudio and
+           maybe WebRTC. */
+        mmcss_handle =
+            AvSetMmThreadCharacteristicsA("Audio", &mmcss_task_index);
+        if (!mmcss_handle) {
+          /* This is not fatal, but we might glitch under heavy load. */
+          LOG("Unable to use mmcss to bump the render thread priority: %lx",
+              GetLastError());
+        } else {
+          LOG("MMCSS render thread promoted (task index %lu)",
+              mmcss_task_index);
+        }
+      } else if (!stm->active && mmcss_handle) {
+        AvRevertMmThreadCharacteristics(mmcss_handle);
+        mmcss_handle = NULL;
+        LOG("MMCSS render thread demoted");
+      }
+      continue;
+    }
+    case WAIT_OBJECT_0 + 2: { /* reconfigure */
       auto_lock lock(stm->stream_reset_lock);
       if (!stm->active) {
         /* Avoid reconfiguring, stream start will handle it. */
@@ -1592,12 +1611,12 @@ static unsigned int __stdcall wasapi_stream_render_loop(LPVOID stream)
       }
       break;
     }
-    case WAIT_OBJECT_0 + 2: /* refill */
+    case WAIT_OBJECT_0 + 3: /* refill */
       XASSERT((has_input(stm) && has_output(stm)) ||
               (!has_input(stm) && has_output(stm)));
       is_playing = stm->refill_callback(stm);
       break;
-    case WAIT_OBJECT_0 + 3: { /* input available */
+    case WAIT_OBJECT_0 + 4: { /* input available */
       bool rv = get_input_buffer(stm);
       if (!rv) {
         is_playing = false;
@@ -2946,6 +2965,12 @@ wasapi_stream_init(cubeb * context, cubeb_stream ** stream,
     return CUBEB_ERROR;
   }
 
+  stm->mmcss_event = CreateEvent(NULL, 0, 0, NULL);
+  if (!stm->mmcss_event) {
+    LOG("Can't create the mmcss event, error: %lx", GetLastError());
+    return CUBEB_ERROR;
+  }
+
   stm->thread_ready_event = CreateEvent(NULL, 0, 0, NULL);
   if (!stm->thread_ready_event) {
     LOG("Can't create the thread ready event, error: %lx", GetLastError());
@@ -3071,6 +3096,7 @@ wasapi_stream_release(cubeb_stream * stm)
     CloseHandle(stm->reconfigure_event);
     CloseHandle(stm->refill_event);
     CloseHandle(stm->input_available_event);
+    CloseHandle(stm->mmcss_event);
 
     CloseHandle(stm->thread);
 
@@ -3167,6 +3193,11 @@ wasapi_stream_start(cubeb_stream * stm)
 
   stm->active = true;
 
+  if (!SetEvent(stm->mmcss_event)) {
+    LOG("wasapi_stream_start: SetEvent(mmcss_event) failed: %lx",
+        GetLastError());
+  }
+
   stm->state_callback(stm, stm->user_ptr, CUBEB_STATE_STARTED);
 
   return CUBEB_OK;
@@ -3199,6 +3230,11 @@ wasapi_stream_stop(cubeb_stream * stm)
 
     stm->active = false;
 
+    if (!SetEvent(stm->mmcss_event)) {
+      LOG("wasapi_stream_stop: SetEvent(mmcss_event) failed: %lx",
+          GetLastError());
+    }
+
     wasapi_state_callback(stm, stm->user_ptr, CUBEB_STATE_STOPPED);
   }