diff --git a/.gitignore b/.gitignore
index a0b491f42789..81a472451d77 100644
--- a/.gitignore
+++ b/.gitignore
@@ -27,6 +27,7 @@ __pycache__/
 /inst/
 /llvm/
 /mingw-build/
+# Created by default with `src/ci/docker/run.sh`:
 /obj/
 /rustllvm/
 /src/libcore/unicode/DerivedCoreProperties.txt
@@ -38,6 +39,8 @@ __pycache__/
 /src/libcore/unicode/UnicodeData.txt
 /src/libcore/unicode/downloaded
 /target/
+# Generated by compiletest for incremental:
+/tmp/
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