diff --git a/tests/functional/fetchGit.sh b/tests/functional/fetchGit.sh
index 492c57602..d98d889a9 100644
--- a/tests/functional/fetchGit.sh
+++ b/tests/functional/fetchGit.sh
@@ -8,6 +8,8 @@ clearStore
 # See https://github.com/NixOS/nix/issues/6195
 repo=$TEST_ROOT/./git
 
+default_branch="$(git config init.defaultBranch)"
+
 export _NIX_FORCE_HTTP=1
 
 rm -rf $repo ${repo}-tmp $TEST_HOME/.cache/nix $TEST_ROOT/worktree $TEST_ROOT/shallow $TEST_ROOT/minimal
@@ -47,7 +49,7 @@ git -C $repo checkout -b devtest
 echo "different file" >> $TEST_ROOT/git/differentbranch
 git -C $repo add differentbranch
 git -C $repo commit -m 'Test2'
-git -C $repo checkout master
+git -C $repo checkout "$default_branch"
 devrev=$(git -C $repo rev-parse devtest)
 out=$(nix eval --impure --raw --expr "builtins.fetchGit { url = \"file://$repo\"; rev = \"$devrev\"; }" 2>&1) || status=$?
 [[ $status == 1 ]]
@@ -118,7 +120,7 @@ path2=$(nix eval --impure --raw --expr "(builtins.fetchGit $repo).outPath")
 [[ $(nix eval --impure --raw --expr "(builtins.fetchGit $repo).dirtyShortRev") = "${rev2:0:7}-dirty" ]]
 
 # ... unless we're using an explicit ref or rev.
-path3=$(nix eval --impure --raw --expr "(builtins.fetchGit { url = $repo; ref = \"master\"; }).outPath")
+path3=$(nix eval --impure --raw --expr "(builtins.fetchGit { url = $repo; ref = \"$default_branch\"; }).outPath")
 [[ $path = $path3 ]]
 
 path3=$(nix eval --raw --expr "(builtins.fetchGit { url = $repo; rev = \"$rev2\"; }).outPath")
diff --git a/tests/functional/fetchGitRefs.sh b/tests/functional/fetchGitRefs.sh
index d643fea04..8a48b6712 100644
--- a/tests/functional/fetchGitRefs.sh
+++ b/tests/functional/fetchGitRefs.sh
@@ -6,6 +6,8 @@ clearStore
 
 repo="$TEST_ROOT/git"
 
+default_branch="$(git config init.defaultBranch)"
+
 rm -rf "$repo" "${repo}-tmp" "$TEST_HOME/.cache/nix"
 
 git init "$repo"
@@ -16,7 +18,7 @@ echo utrecht > "$repo"/hello
 git -C "$repo" add hello
 git -C "$repo" commit -m 'Bla1'
 
-path=$(nix eval --raw --impure --expr "(builtins.fetchGit { url = $repo; ref = \"master\"; }).outPath")
+path=$(nix eval --raw --impure --expr "(builtins.fetchGit { url = $repo; ref = \"$default_branch\"; }).outPath")
 
 # Test various combinations of ref names
 # (taken from the git project)
@@ -38,7 +40,7 @@ path=$(nix eval --raw --impure --expr "(builtins.fetchGit { url = $repo; ref = \
 valid_ref() {
     { set +x; printf >&2 '\n>>>>>>>>>> valid_ref %s\b <<<<<<<<<<\n' $(printf %s "$1" | sed -n -e l); set -x; }
     git check-ref-format --branch "$1" >/dev/null
-    git -C "$repo" branch "$1" master >/dev/null
+    git -C "$repo" branch "$1" "$default_branch" >/dev/null
     path1=$(nix eval --raw --impure --expr "(builtins.fetchGit { url = $repo; ref = ''$1''; }).outPath")
     [[ $path1 = $path ]]
     git -C "$repo" branch -D "$1" >/dev/null
diff --git a/tests/functional/flakes/flakes.sh b/tests/functional/flakes/flakes.sh
index 75cc329e5..f41dc365a 100644
--- a/tests/functional/flakes/flakes.sh
+++ b/tests/functional/flakes/flakes.sh
@@ -3,6 +3,9 @@ source ./common.sh
 requireGit
 
 clearStore
+
+default_branch="$(git config init.defaultBranch)"
+
 rm -rf $TEST_HOME/.cache $TEST_HOME/.config
 
 flake1Dir=$TEST_ROOT/flake1
@@ -15,10 +18,10 @@ badFlakeDir=$TEST_ROOT/badFlake
 flakeGitBare=$TEST_ROOT/flakeGitBare
 
 for repo in $flake1Dir $flake2Dir $flake3Dir $flake7Dir $nonFlakeDir; do
-    # Give one repo a non-main initial branch.
+    # Give one repo a non-default initial branch.
     extraArgs=
     if [[ $repo == $flake2Dir ]]; then
-      extraArgs="--initial-branch=main"
+      extraArgs="--initial-branch=notdefault"
     fi
 
     createGitRepo "$repo" "$extraArgs"
@@ -152,11 +155,11 @@ nix build -o $TEST_ROOT/result $flake2Dir#bar --no-write-lock-file
 expect 1 nix build -o $TEST_ROOT/result $flake2Dir#bar --no-update-lock-file 2>&1 | grep 'requires lock file changes'
 nix build -o $TEST_ROOT/result $flake2Dir#bar --commit-lock-file
 [[ -e $flake2Dir/flake.lock ]]
-[[ -z $(git -C $flake2Dir diff main || echo failed) ]]
+[[ -z $(git -C $flake2Dir diff notdefault || echo failed) ]]
 
 # Rerunning the build should not change the lockfile.
 nix build -o $TEST_ROOT/result $flake2Dir#bar
-[[ -z $(git -C $flake2Dir diff main || echo failed) ]]
+[[ -z $(git -C $flake2Dir diff notdefault || echo failed) ]]
 
 # Building with a lockfile should not require a fetch of the registry.
 nix build -o $TEST_ROOT/result --flake-registry file:///no-registry.json $flake2Dir#bar --refresh
@@ -165,7 +168,7 @@ nix build -o $TEST_ROOT/result --no-use-registries $flake2Dir#bar --refresh
 
 # Updating the flake should not change the lockfile.
 nix flake lock $flake2Dir
-[[ -z $(git -C $flake2Dir diff main || echo failed) ]]
+[[ -z $(git -C $flake2Dir diff notdefault || echo failed) ]]
 
 # Now we should be able to build the flake in pure mode.
 nix build -o $TEST_ROOT/result flake2#bar
@@ -200,7 +203,7 @@ nix build -o $TEST_ROOT/result $flake3Dir#"sth sth"
 nix build -o $TEST_ROOT/result $flake3Dir#"sth%20sth"
 
 # Check whether it saved the lockfile
-[[ -n $(git -C $flake3Dir diff master) ]]
+[[ -n $(git -C $flake3Dir diff "$default_branch") ]]
 
 git -C $flake3Dir add flake.lock
 
@@ -286,7 +289,7 @@ nix build -o $TEST_ROOT/result $flake3Dir#sth --commit-lock-file
 Flake lock file updates:
 
 "?" Added input 'nonFlake':
-    'git+file://"*"/flakes/flakes/nonFlake?ref=refs/heads/master&rev="*"' "*"
+    'git+file://"*"/flakes/flakes/nonFlake?ref=refs/heads/$default_branch&rev="*"' "*"
 "?" Added input 'nonFlakeFile':
     'path:"*"/flakes/flakes/nonFlake/README.md?lastModified="*"&narHash=sha256-cPh6hp48IOdRxVV3xGd0PDgSxgzj5N/2cK0rMPNaR4o%3D' "*"
 "?" Added input 'nonFlakeFile2':
@@ -313,10 +316,10 @@ nix build -o $TEST_ROOT/result flake4#xyzzy
 
 # Test 'nix flake update' and --override-flake.
 nix flake lock $flake3Dir
-[[ -z $(git -C $flake3Dir diff master || echo failed) ]]
+[[ -z $(git -C $flake3Dir diff "$default_branch" || echo failed) ]]
 
 nix flake update --flake "$flake3Dir" --override-flake flake2 nixpkgs
-[[ ! -z $(git -C "$flake3Dir" diff master || echo failed) ]]
+[[ ! -z $(git -C "$flake3Dir" diff "$default_branch" || echo failed) ]]
 
 # Make branch "removeXyzzy" where flake3 doesn't have xyzzy anymore
 git -C $flake3Dir checkout -b removeXyzzy
@@ -350,7 +353,7 @@ EOF
 nix flake lock $flake3Dir
 git -C $flake3Dir add flake.nix flake.lock
 git -C $flake3Dir commit -m 'Remove packages.xyzzy'
-git -C $flake3Dir checkout master
+git -C $flake3Dir checkout "$default_branch"
 
 # Test whether fuzzy-matching works for registry entries.
 (! nix build -o $TEST_ROOT/result flake4/removeXyzzy#xyzzy)
@@ -499,7 +502,7 @@ nix flake lock $flake3Dir --override-input flake2/flake1 file://$TEST_ROOT/flake
 nix flake lock $flake3Dir --override-input flake2/flake1 flake1
 [[ $(jq -r .nodes.flake1_2.locked.rev $flake3Dir/flake.lock) =~ $hash2 ]]
 
-nix flake lock $flake3Dir --override-input flake2/flake1 flake1/master/$hash1
+nix flake lock $flake3Dir --override-input flake2/flake1 "flake1/$default_branch/$hash1"
 [[ $(jq -r .nodes.flake1_2.locked.rev $flake3Dir/flake.lock) =~ $hash1 ]]
 
 nix flake lock $flake3Dir
@@ -510,8 +513,8 @@ nix flake update flake2/flake1 --flake "$flake3Dir"
 [[ $(jq -r .nodes.flake1_2.locked.rev "$flake3Dir/flake.lock") =~ $hash2 ]]
 
 # Test updating multiple inputs.
-nix flake lock "$flake3Dir" --override-input flake1 flake1/master/$hash1
-nix flake lock "$flake3Dir" --override-input flake2/flake1 flake1/master/$hash1
+nix flake lock "$flake3Dir" --override-input flake1 "flake1/$default_branch/$hash1"
+nix flake lock "$flake3Dir" --override-input flake2/flake1 "flake1/$default_branch/$hash1"
 [[ $(jq -r .nodes.flake1.locked.rev "$flake3Dir/flake.lock") =~ $hash1 ]]
 [[ $(jq -r .nodes.flake1_2.locked.rev "$flake3Dir/flake.lock") =~ $hash1 ]]