diff --git a/.gitignore b/.gitignore
index b4d0b12..dc927be 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,6 @@ target/
 .metals
 .vscode
 metals.sbt
+
+# simplest portable 'sed -i' syntax creates backup files, eg 'sed -i.bak' - see https://unix.stackexchange.com/a/92907/46453
+*.bak
\ No newline at end of file
diff --git a/sbt-version-policy/src/sbt-test/sbt-version-policy/example-sbt-ci-release/test b/sbt-version-policy/src/sbt-test/sbt-version-policy/example-sbt-ci-release/test
index 306065a..c53b604 100644
--- a/sbt-version-policy/src/sbt-test/sbt-version-policy/example-sbt-ci-release/test
+++ b/sbt-version-policy/src/sbt-test/sbt-version-policy/example-sbt-ci-release/test
@@ -5,7 +5,7 @@ $ exec git config user.name "name"
 
 # Before first release, set `versionPolicyIntention` to `Compatibility.None` because
 # there is no previous release to compare to.
-$ exec sed -i 's/versionPolicyIntention := .*/versionPolicyIntention := Compatibility.None/' build.sbt
+$ exec sed -i.bak 's/versionPolicyIntention := .*/versionPolicyIntention := Compatibility.None/' build.sbt
 
 $ exec git add .
 $ exec git commit -m "Initial commit"
@@ -18,7 +18,7 @@ $ exec git tag v1.0.0
 > ci-release
 
 # Reset compatibility intention after release
-$ exec sed -i 's/versionPolicyIntention := .*/versionPolicyIntention := Compatibility.BinaryAndSourceCompatible/' build.sbt
+$ exec sed -i.bak 's/versionPolicyIntention := .*/versionPolicyIntention := Compatibility.BinaryAndSourceCompatible/' build.sbt
 
 # New contributions
 $ exec git commit -a -m "Some hard work"
diff --git a/sbt-version-policy/src/sbt-test/sbt-version-policy/example-sbt-dynver/test b/sbt-version-policy/src/sbt-test/sbt-version-policy/example-sbt-dynver/test
index 1f08521..d957eb4 100644
--- a/sbt-version-policy/src/sbt-test/sbt-version-policy/example-sbt-dynver/test
+++ b/sbt-version-policy/src/sbt-test/sbt-version-policy/example-sbt-dynver/test
@@ -13,7 +13,7 @@ $ exec git tag v1.0.0
 > publishLocal
 
 # Reset compatibility intention after release
-$ exec sed -i 's/versionPolicyIntention := .*/versionPolicyIntention := Compatibility.BinaryAndSourceCompatible/' build.sbt
+$ exec sed -i.bak 's/versionPolicyIntention := .*/versionPolicyIntention := Compatibility.BinaryAndSourceCompatible/' build.sbt
 
 # New contributions
 $ exec git commit -a -m "Some hard work"