diff --git a/env.ps1 b/env.ps1
index b5d4721..8887b87 100644
--- a/env.ps1
+++ b/env.ps1
@@ -31,3 +31,4 @@
 Function Global:dotest_ci { pytest -q -n auto --hypothesis-profile=ci }
 Function Global:dotest_long { pytest -q -n auto --hypothesis-profile=long }
 Function Global:docheck { dotidy && dolint && dotest }
+Function Global:domut { mutmut run --paths-to-mutate "src/syntax.py src/tokenize.py src/parse.py" }
diff --git a/env.sh b/env.sh
index b763209..3be4998 100644
--- a/env.sh
+++ b/env.sh
@@ -30,3 +30,4 @@
 dotest_ci() { pytest -q -n auto --hypothesis-profile=ci; }
 dotest_long() { pytest -q -n auto --hypothesis-profile=long; }
 docheck() { dotidy && dolint && dotest; }
+domut() { mutmut run --paths-to-mutate "src/syntax.py src/tokenize.py src/parse.py"; }