diff --git a/hooks/prepare-commit-msg b/hooks/prepare-commit-msg
index 538557a..b779506 100755
--- a/hooks/prepare-commit-msg
+++ b/hooks/prepare-commit-msg
@@ -4,23 +4,24 @@
 # When on a branch referring to a Jira issue,
 # ensure commit messages start with the issue reference
 
+# Allow skipping
+case ${SKIP:-} in *prepare-commit-msg*) exit 0 ;; esac
+
+# Don't alter fixup messages
+grep -q "^fixup! " "$1" && exit 0
+
 JIRA_CODE_PATTERN=${JIRA_CODE_PATTERN:-$(git config --get mr.jira-code-pattern)}
 if [ -z "$JIRA_CODE_PATTERN" ]; then
     echo "JIRA_CODE_PATTERN not set - unable to guess issue code" >&2
     exit 0
 fi
 
+# Exit if code already present in message header
+head -n 1 "$1" | grep -Eiq "$JIRA_CODE_PATTERN" && exit 0
+
 current_branch=$(git rev-parse --abbrev-ref HEAD)
 issue_code=$(echo "${current_branch}" | grep -Eo "$JIRA_CODE_PATTERN" | tail -n1)
 [ -n "$issue_code" ] || exit 0 # No issue code detected
 
-current_msg=$(cat "$1")
-msg_code=$(echo "${current_msg}" | grep -iEo "$JIRA_CODE_PATTERN" | tail -n1)
-[ -z "$msg_code" ] || exit 0 # existing issue code in message
-
-if case "$current_msg" in "fixup! "*) ;; *) false;; esac; then
-    exit 0 # don't alter fixup messages
-fi
-
 echo "Prefixing message with issue code: $issue_code" >&2
 sed -i.bak -e "1s/^/$issue_code /" "$1"
diff --git a/test/git-mr.bats b/test/git-mr.bats
index fe90626..78cd7f3 100644
--- a/test/git-mr.bats
+++ b/test/git-mr.bats
@@ -2715,7 +2715,17 @@ n'
     assert_line "Prefixing message with issue code: AB-123"
     assert_line "[feature/AB-123-test-feature $(git rev-parse --short HEAD)] AB-123 Test message 2"
 
-    git reset --hard HEAD~2
+    run git commit --allow-empty --fixup HEAD~1
+    refute_line "Prefixing message with issue code: AB-123"
+    assert_line "[feature/AB-123-test-feature $(git rev-parse --short HEAD)] fixup! Test message 1"
+
+    run git commit --allow-empty -m "XY-456 Test message 3"
+    refute_line "Prefixing message with issue code: AB-123"
+    assert_line "[feature/AB-123-test-feature $(git rev-parse --short HEAD)] XY-456 Test message 3"
+
+    # standard .git directory - teardown
+    git reset --hard HEAD~4
+    rm -f .git/hooks/prepare-commit-msg
 
     # submodule
 
@@ -2738,4 +2748,26 @@ n'
     run git commit --allow-empty -m "Sub message 2"
     assert_line "Prefixing message with issue code: XY-345"
     assert_line "[feature/XY-345-test $(git rev-parse --short HEAD)] XY-345 Sub message 2"
+
+    # submodule - teardown
+    cd "${BATS_TEST_DIRNAME}/data" || exit
+    cd repo; git submodule deinit -f sub; cd ..
+    rm -rf subrepo repo/sub repo/.gitmodules repo/.git/modules
+}
+
+@test "pre-commit-msg hook can be skipped" {
+    # setup
+    git-mr hook
+
+    run git commit --allow-empty -m "Test prefixed message"
+    assert_line "Prefixing message with issue code: AB-123"
+    assert_line "[feature/AB-123-test-feature $(git rev-parse --short HEAD)] AB-123 Test prefixed message"
+
+    SKIP=aaa,prepare-commit-msg,zzz run git commit --allow-empty -m "Test unprefixed message"
+    refute_line "Prefixing message with issue code: AB-123"
+    assert_line "[feature/AB-123-test-feature $(git rev-parse --short HEAD)] Test unprefixed message"
+
+    # teardown
+    git reset --hard HEAD~2
+    rm -f .git/hooks/prepare-commit-msg
 }