diff --git a/TSPL.docc/LanguageGuide/Concurrency.md b/TSPL.docc/LanguageGuide/Concurrency.md
index 007462a53..072c79051 100644
--- a/TSPL.docc/LanguageGuide/Concurrency.md
+++ b/TSPL.docc/LanguageGuide/Concurrency.md
@@ -1107,8 +1107,8 @@ the code below converts measured temperatures from Fahrenheit to Celsius:
 ```swift
 extension TemperatureLogger {
     func convertFahrenheitToCelsius() {
-        measurements = measurements.map { measurement in
-            (measurement - 32) * 5 / 9
+        for i in measurements.indices {
+            measurements[i] =  (measurements[i] - 32) * 5 / 9
         }
     }
 }