diff --git a/java/libraries/io/src/processing/io/PWM.java b/java/libraries/io/src/processing/io/PWM.java
index 7c2406dcf..6ea050a11 100644
--- a/java/libraries/io/src/processing/io/PWM.java
+++ b/java/libraries/io/src/processing/io/PWM.java
@@ -157,17 +157,19 @@ public class PWM {
   public void set(int period, float duty) {
     // set period
     String fn = fn = String.format("/sys/class/pwm/%s/pwm%d/period", chip, channel);
+    // convert to nanoseconds
     int ret = NativeInterface.writeFile(fn, String.format("%d", (int)(1000000000 / period)));
     if (ret < 0) {
       throw new RuntimeException(fn + ": " + NativeInterface.getError(ret));
     }
 
     // set duty cycle
-    fn = fn = String.format("/sys/class/pwm/%s/pwm%d/duty", chip, channel);
+    fn = fn = String.format("/sys/class/pwm/%s/pwm%d/duty_cycle", chip, channel);
     if (duty < 0.0 || 1.0 < duty) {
       System.err.println("Duty cycle must be between 0.0 and 1.0.");
       throw new IllegalArgumentException("Illegal argument");
     }
+    // convert to nanoseconds
     ret = NativeInterface.writeFile(fn, String.format("%d", (int)((1000000000 * duty) / period)));
     if (ret < 0) {
       throw new RuntimeException(fn + ": " + NativeInterface.getError(ret));