diff --git a/docs/errata/README.md b/docs/errata/README.md
index 8e2d1b4..5676d8e 100644
--- a/docs/errata/README.md
+++ b/docs/errata/README.md
@@ -4,6 +4,6 @@ If you find any mistakes in the seventh edition, *C# 11 and .NET 7 - Modern Cros
 
 [**Errata** (34 items)](errata.md): Typos, tool user interface changes, or mistakes in code that would cause a compilation error that prevents a successful build.
 
-[**Improvements** (17 items)](improvements.md): Changes to text or code that would improve the content. These are optional.
+[**Improvements** (18 items)](improvements.md): Changes to text or code that would improve the content. These are optional.
 
 All errata and improvements will be included in the 8th edition planned for publishing in November 2023. To be included they must be submitted by mid-September 2023.
diff --git a/docs/errata/improvements.md b/docs/errata/improvements.md
index d4f1395..2ace223 100644
--- a/docs/errata/improvements.md
+++ b/docs/errata/improvements.md
@@ -1,4 +1,4 @@
-**Improvements** (17 items)
+**Improvements** (18 items)
 
 If you have suggestions for improvements, then please [raise an issue in this repository](https://github.com/markjprice/cs11dotnet7/issues) or email me at markjprice (at) gmail.com.
 
@@ -7,6 +7,7 @@ If you have suggestions for improvements, then please [raise an issue in this re
 - [Page 128 - Rounding numbers](#page-128---rounding-numbers)
 - [Page 149 - Writing a times table function](#page-149---writing-a-times-table-function)
 - [Page 153 - Writing a function that returns a value](#page-153---writing-a-function-that-returns-a-value)
+- [Page 161 - Using lambdas in function implementations](#page-161---using-lambdas-in-function-implementations)
 - [Page 179 - Reviewing project packages](#page-179---reviewing-project-packages)
 - [Page 237 - Implementing functionality using methods](#page-237---implementing-functionality-using-methods)
 - [Page 251 - Setting up a class library and console application](#page-251---setting-up-a-class-library-and-console-application)
@@ -112,6 +113,12 @@ Add the following statement near the top of the code file before doing any writi
 Console.OutputEncoding = System.Text.Encoding.UTF8;
 ```
 
+# Page 161 - Using lambdas in function implementations
+
+> Thanks to [Masoud Nazari](https://github.com/MAS-OUD) for raising this [issue on 8 March 2023](https://github.com/markjprice/cs11dotnet7/issues/39).
+
+In the next edition, I will expand on the definition of **Immutability** e.g. a data value that cannot change. I will also note that C# `record` types are not necessarily immutable.
+
 # Page 179 - Reviewing project packages
 
 In Step 1, the instruct the reader to add references to four packages, as shown in the following markup: