diff --git a/README.md b/README.md
index fac1b77..c20f4ec 100644
--- a/README.md
+++ b/README.md
@@ -251,8 +251,6 @@ view `coverage/index.html` in a browser.
 
  0. implement WASAPI (Windows) backend, get examples working
     - list devices
-      - raw mode
-        - period duration
       - watching
     - sine wave
     - microphone
diff --git a/soundio/soundio.h b/soundio/soundio.h
index dc7e9f5..c8ba5f3 100644
--- a/soundio/soundio.h
+++ b/soundio/soundio.h
@@ -364,9 +364,12 @@ struct SoundIoDevice {
     double buffer_duration_current;
 
     // Period duration in seconds. After this much time passes, write_callback
-    // is called. If values are unknown, they are set to 0.0. These values are
-    // meaningless for PulseAudio and CoreAudio. For JACK, buffer duration and
-    // period duration are the same.
+    // is called. If values are unknown, they are set to 0.0.
+    // For PulseAudio and CoreAudio, these values are meaningless.
+    // For JACK, buffer duration and period duration are the same.
+    // For WASAPI, `period_duration_max` is unknown for raw devices, so a
+    // reasonable max of 4.0 is used. You may check that the current backend is
+    // WASAPI and ignore the max value for raw devices.
     double period_duration_min;
     double period_duration_max;
     double period_duration_current;
diff --git a/src/wasapi.cpp b/src/wasapi.cpp
index 07c537b..21a3c10 100644
--- a/src/wasapi.cpp
+++ b/src/wasapi.cpp
@@ -650,7 +650,11 @@ static int refresh_devices(SoundIoPrivate *si) {
             return SoundIoErrorOpeningDevice;
         }
         rd.device_shared->period_duration_current = from_reference_time(default_device_period);
-        rd.device_shared->period_duration_min = from_reference_time(min_device_period);
+        rd.device_shared->period_duration_min = rd.device_shared->period_duration_current;
+        rd.device_shared->period_duration_max = rd.device_shared->period_duration_current;
+
+        rd.device_raw->period_duration_min = from_reference_time(min_device_period);
+        rd.device_raw->period_duration_max = 4.0;
 
 
         if (rd.endpoint)