diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 8bd1ab2e7..56ce976d6 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -5,5 +5,6 @@ If your are considering creating a pull request, please observe the following:
 - If you are adding or modifying a feature, add *new* unit tests that test that feature.
 - If you are fixing a bug, add a unit test that *fails* before the bug fix is implemented.
 - Do not initiate a pull request until all of the units tests pass.
+- Branches should be based on the branch `master`.
 
 There is a project file for VS2022 for C++14, 17, 20, and bash scripts that run the tests for C++11, 14, 17, 20 under Linux with GCC and Clang.