diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 31cf38679..c81c0d4db 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -77,8 +77,10 @@ processed incorrectly by a type checker. It is also helpful to add
 links to online documentation or to the implementation of the code
 you are changing.
 
-Also, do not squash your commits after you have submitted a pull request, as this
+Also, do not squash your commits or use `git commit --amend` after you have submitted a pull request, as this
 erases context during review. We will squash commits when the pull request is merged.
+This way, your pull request will appear as a single commit in our git history, even
+if it consisted of several smaller commits.
 
 At present the maintainers are (alphabetically):
 * David Fisher (@ddfisher)