diff --git a/.coveragerc b/.coveragerc
index f03a13c..6449c64 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -3,7 +3,7 @@ branch = True
 include =
   amaranth/*
 omit =
-  amaranth/test/*
+  tests/*
 
 [report]
 exclude_lines =
diff --git a/CONTRIBUTING.txt b/CONTRIBUTING.txt
index 444e81c..f41dd63 100644
--- a/CONTRIBUTING.txt
+++ b/CONTRIBUTING.txt
@@ -4,6 +4,9 @@ We love contributions from the community. Please send pull requests and raise
 issues! All code submissions require review. We use GitHub pull requests for
 this purpose.
 
+See the "Contributing" section of the documentation manual for more details
+about contributing to Amaranth.
+
 
 COPYRIGHTS and LICENSE
 
diff --git a/pyproject.toml b/pyproject.toml
index 3c79674..7049cae 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -46,6 +46,13 @@ build-backend = "pdm.backend"
 # Add a workaround to improve experience for people upgrading from old checkouts.
 includes = ["amaranth/"]
 
+source-includes = [
+  ".gitignore",
+  ".coveragerc",
+  ".env.toolchain",
+  "CONTRIBUTING.txt",
+]
+
 # Development workflow configuration
 
 [tool.pdm.dev-dependencies]