diff --git a/.gitignore b/.gitignore
index 9bad20a3..f6d8b99b 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,7 +4,8 @@
 ## Get latest from https://github.com/github/gitignore/blob/main/VisualStudio.gitignore
 
 # Manually-added items
-/src/Mathematics.NET.DevApp/*.cs
+/src/Mathematics.NET.DevApp/*
+!/src/Mathematics.NET.DevApp/Mathematics.NET.DevApp.csproj
 !/src/Mathematics.NET.DevApp/Program.cs
 *.runsettings