diff --git a/README.md b/README.md
index 09ddd23..331c911 100644
--- a/README.md
+++ b/README.md
@@ -164,9 +164,9 @@ led = Pin(5, Pin.OUT)
 
 def callback(timer):
     global data, index
-    data[index] = utime.ticks_ms
+    data[index] = utime.ticks_ms()
     index = (index + 1) % 32
-    led(!led())
+    led(not led())
 
 # Run the callback once, after 100 ms
 timer.init(mode = Timer.ONE_SHOT, period = 100, callback = callback)